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  • 101.
    Edvinsson, Sören
    et al.
    Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).
    Broström, Göran
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Old age, health and social inequality: exploring the social patterns of mortality in 19th Century Northern Sweden2012In: Demographic Research, ISSN 1435-9871, Vol. 26, p. 23-Article in journal (Refereed)
    Abstract [en]

    BACKGROUND

    Social position is one of the major determinants of health. Less is known about its effect in historical contexts. Previous studies have shown surprisingly small effects of social class in working age populations. Not much is known about social differences in health among the elderly in history.

    OBJECTIVE

    The present paper analyses social differences in health among the elderly (60+) in the Sundsvall region in northern Sweden during the 19th century. We investigate whether social mortality differences are particularly apparent in old age when unpropertied groups lost their most important asset for survival: their capacity to work.

    METHODS

    The data, representing 9,535 fatal events, are analysed using a Cox regression model, assuming proportional hazards.

    RESULTS

    Social class had no significant effect for women during the pre-industrial period, while only those with unknown social position had higher mortality among men. During the industrial period female mortality was lowest in the skilled working class and highest in the upper class. Social position was not significant for men in the full model. Urban mortality was 30% higher for women and 59% higher for men during the pre-industrial period compared to the peripheral parishes.

    CONCLUSIONS

    The results lead us to question the accepted 'fact' of social health differences as a historical constant. Higher social position did not lead to better survival, and social differences in mortality did not increase in old age, despite the fact that the elderly were a highly vulnerable group. Instead, the spatial aspects of mortality were important, particularly during the pre-industrial period.

  • 102.
    Edvinsson, Sören
    et al.
    Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).
    Häggström Lundevaller, Erling
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Malmberg, Gunnar
    Umeå University, Faculty of Social Sciences, Department of Geography and Economic History, Economic and social geography.
    Do unequal societies cause death among the elderly?: a study of the health effects of inequality in Swedish municipalities, 20062013In: Global Health Action, ISSN 1654-9716, E-ISSN 1654-9880, Vol. 6, no 1, article id 19116Article in journal (Refereed)
    Abstract [en]

    Background: A lively public and academic debate has highlighted the potential health risk of living in regions and nations characterized by inequality. However, previous research provides an ambiguous picture, with positive association mainly having been found on higher geographical levels. One explanation for this could be that the effect of living in more heterogeneous social settings differs between levels of aggregation. 

    Methods: We examine the association between income inequality (using the Gini coefficient) and all-cause mortality in Swedish municipalities in the age group 65-74. A multi-level analysis is applied and we control for e.g. individual income and average income level in the unicipality. The analyses are based on individual register data on all residents born between 1932 and 1941, and outcomes are measured for the year 2006.

    Results: Lower individual income as well as lower average income level in the municipality of residence increased mortality significantly. We found an association between income inequality and mortality with excessive deaths in unequal municipalities even after controlling for mean income level and personal income. The results from the analysis of individual data differed substantially from analyses using aggregate data.

    Conclusions: Income inequality has a significant association with mortality in the age groups 65 to 75 at municipality level. The association is small compared to many other variables, but it is not negligible. Even in a comparatively equal society like Sweden, we need to consider possible effects of income inequality on mortality at the local level. 

  • 103.
    Edvinsson, Sören
    et al.
    Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).
    Lindkvist, Marie
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Wealth and health in 19th century Sweden: A study of social differences in adult mortality in the Sundsvall Region2011In: Explorations in economic history (Print), ISSN 0014-4983, E-ISSN 1090-2457, Vol. 48, no 3, p. 376-388Article in journal (Refereed)
    Abstract [en]

    The present article analyses social inequality in mortality in the 19th century Sundsvall region, an area that experienced rapid industrialization after 1850. The purpose of the study is to investigate whether there were social differences in mortality in this context and whether these differences increased during the industrial break-through. The expected advantages for higher social classes could not be confirmed in this environment. Instead, the best survival was found among those belonging to the agricultural sector. We found a strongly gendered pattern, with much higher mortality for and small health differences among men, while the results indicate increasing social inequality in female mortality during industrialization. The spatial pattern of mortality was pronounced and living with a partner had a strong impact on survival, particularly for men. We finally discuss the role of gender and class expectations in relation to lifestyles for the social patterning of mortality.

  • 104.
    Edvinsson, Sören
    et al.
    Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).
    Malmberg, Gunnar
    Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS). Umeå University, Faculty of Social Sciences, Department of Geography and Economic History.
    Häggström Lundevaller, Erling
    Umeå University, Faculty of Social Sciences, Department of Statistics. Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).
    Do unequal societies cause death and disease?: A study of the health effects on elderly of inequality in Swedish municipalities, 20062011Report (Other academic)
    Abstract [en]

    A lively public and academic debate has highlighted the potential health risk of living in regions and nations characterized by inequality (Wilkinson and Pickett 2007; 2009). It is argued that inequality may add to increasing health differentials over the life course. However, previous research provides so far an ambiguous picture. One explanation could be that the effect of living in more heterogeneous social settings may differ between levels of aggregation. A hypothesis is that homogeneity is positive on the national or regional level, while on a lower level of aggregation living in homogeneous settings could be detrimental for health, at least in poor neighborhoods.

    In this paper we present the preliminary results of our examination on how residence in unequal versus homogeneous areas is associated with health outcome of elderly people in Sweden. These first results are based on municipality level data on individuals born between 1932 and 1941 and the outcome is measured for the year 2006. Furthermore, we analyze the effect on health of income inequality (measured by Gini-coefficient) as compared to the effect of individual income and the average income level in the area. We analysed the associations both with individual-level and multi-level analysis. Our main finding is that inequality has an independent effect on mortality in the way that unequal municipalities have excessive deaths even after controlling for mean income level and personal income. This result was found not only in the individual-level analysis but also in the multilevel analysis.

  • 105.
    Elezovic, Suad
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Estimating quadratic variation of prices and spreads from the Swedish limit order bookManuscript (Other academic)
    Abstract [en]

    The realized quadratic variation is considered to be a suitable measure of volatility of financial prices since it has been shown to  be a consistent non-parametric estimator of  the increments of  quadratic variation. In the approach presented here, measuring volatility of the prices and returns from the Swedish high-frequency limit order book data by means of a non-parametric estimator is extended  to  measuring volatility from the bid and ask  curves. Since they are  functions of both prices and quantities, these curves are likely to be more informative about volatility  than the ordinary bid and ask prices.  In particular, finding  an optimal time interval for computations of the squared  returns is a crucial step in creating more precise estimators of volatility. The main results  confirm the  empirical results from some other comparable studies about  microstructure effects: The bias of the proposed  estimator increases as the interpolation time interval approaches zero. In contrast to previous studies made on more liquid markets, the major reduction of microstructure noise is only obtained when the sampling frequency is fairly low.

  • 106.
    Elezovic, Suad
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Evaluation of two-step estimation procedure for a functional model of volatilityManuscript (Other academic)
    Abstract [en]

    A two-step  procedure for volatility estimation is evaluated by a simulation study intended to mimic estimation from the  Swedish limit order book. To simulate data with varying volatility the Heston stochastic volatility model is used. From the simulated data, the time series of realized quadratic variation (RQV) for a given relative quantity of shares are obtained. These time series are modeled in a functional time series context by fitting an autoregressive moving average model. This model may be estimated in two ways, either by obtaining the raw estimates of the coefficient functions (naive approach) or by smoothing the fitted coefficient functions (two-step approach). Our  results show that  the risk measures of the smooth coefficient functions are indeed smaller than the corresponding risk measures of the coefficient functions of raw estimates. Consequently, the two-step estimation procedure is  considered to be  more efficient than the naive approach within this framework.

  • 107.
    Elezovic, Suad
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Functional modelling of volatility in the Swedish limit order book market2008In: Computational Statistics & Data Analysis, ISSN 0167-9473, E-ISSN 1872-7352Article in journal (Refereed)
    Abstract [en]

    The publicly available electronic limit order book at the StockholmStock Exchange consists of five levels of prices and quantities of agiven stock with a bid and ask side. All changes in the book duringone day can be recorded with a time quote. Studying variation of the quoted price returns as function of quantity is discussed. In particular, discovering and modelling dynamic behaviours in thevolatility of prices and liquidity measures are considered. Applying a functional approach, estimation of the volatility dynamics of the spreads, created as differences between the ask and bid prices, is presented through a case study. For thatpurpose  two-step estimation of functional linear models is used, extending this method to atime series context.

  • 108.
    Elezovic, Suad
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Modeling financial volatility: A functional approach with applications to Swedish limit order book data2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is designed to offer an approach to modeling volatility in the Swedish limit order market. Realized quadratic variation is used as an estimator of the integrated variance, which is a measure of the variability of a stochastic process in continuous time. Moreover, a functional time series model for the realized quadratic variation is introduced. A two-step estimation procedure for such a model is then proposed. Some properties of the proposed two-step estimator are discussed and illustrated through an application to high-frequency financial data and simulated experiments.

    In Paper I, the concept of realized quadratic variation, obtained from the bid and ask curves, is presented. In particular, an application to the Swedish limit order book data is performed using signature plots to determine an optimal sampling frequency for the computations. The paper is the first study that introduces realized quadratic variation in a functional context.

    Paper II introduces functional time series models and apply them to the modeling of volatility in the Swedish limit order book. More precisely, a functional approach to the estimation of volatility dynamics of the spreads (differences between the bid and ask prices) is presented through a case study. For that purpose, a two-step procedure for the estimation of functional linear models is adapted to the estimation of a functional dynamic time series model.

    Paper III studies a two-step estimation procedure for the functional models introduced in Paper II. For that purpose, data is simulated using the Heston stochastic volatility model, thereby obtaining time series of realized quadratic variations as functions of relative quantities of shares. In the first step, a dynamic time series model is fitted to each time series. This results in a set of inefficient raw estimates of the coefficient functions. In the second step, the raw estimates are smoothed. The second step improves on the first step since it yields both smooth and more efficient estimates. In this simulation, the smooth estimates are shown to perform better in terms of mean squared error.

    Paper IV introduces an alternative to the two-step estimation procedure mentioned above. This is achieved by taking into account the correlation structure of the error terms obtained in the first step. The proposed estimator is based on seemingly unrelated regression representation. Then, a multivariate generalized least squares estimator is used in a first step and its smooth version in a second step. Some of the asymptotic properties of the resulting two-step procedure are discussed. The new procedure is illustrated with functional high-frequency financial data.

  • 109.
    Elezovic, Suad
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    A note on the estimation of functional autoregressive modelsManuscript (Other academic)
    Abstract [en]

    Consider situations where a real valued function is observed over time and has a dynamic dependence structure. Linear autoregressive models, which have been proven useful to model dynamics of "pointwise" time series, can be generalized to such a functional time series situation. We call such models functional autoregressive models. Their parameters are functions of a real valued argument (as the data) and we consider a two-step estimation procedure inspired by Fan and Zhang's (2000) proposal for functional linear models. The latter proposal is based on a first step where the ordinary least squares is used to estimate pointwise linear models for given values of the argument of the functions observed. The second step smoothes the first-step estimates, regressing the latter on the mentioned arguments. The second step does not only yield smooth estimates of the functional parameters but also provides less variable pointwise estimates at the price of a bias. We do not only contribute  by presenting an autoregressive model for functional data but also by proposing a two-stage estimator where the first step takes into account the contemporaneous correlation structure through a multivariate generalized least squares estimator. Some of the properties of the resulting two-step procedure are given. Financial functional data is used as an illustration.

  • 110.
    Eurenius, Eva
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Lindkvist, Marie
    Umeå University, Faculty of Social Sciences, Department of Statistics. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Sundqvist, Magdalena
    Ivarsson, Anneli
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Mogren, Ingrid
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Obstetrics and Gynaecology.
    Maternal and paternal self-rated health and BMI in relation to lifestyle in early pregnancy: The Salut Programme in Sweden2011In: Scandinavian Journal of Public Health, ISSN 1403-4948, E-ISSN 1651-1905, Vol. 39, no 7, p. 730-741Article in journal (Refereed)
    Abstract [en]

    Aim: This study’s aim was to increase knowledge about maternal and paternal self-rated health and body mass index in relation to lifestyle during early pregnancy. Methods: Study subjects were expectant parents visiting antenatal care (2006—07) as part of the Salut Programme in northern Sweden. During early pregnancy, 468 females and 413 male partners completed questionnaires. The questions addressed sociodemography, self-rated general health, weight and height, satisfaction with weight, and lifestyle, such as dietary habits, physical activity, sleeping pattern, and alcohol, tobacco, and drug use. Results: Most rated their general health as good, very good, or excellent, although women less often than men (88% and 93%). The sex difference was more prominent when restricting the comparison to self-rated health being very good or excellent - 49% of the women compared to 61% of the men. Being overweight or obese was common (53% of the men and 30% of the women). Few participants fulfilled the national recommendations with respect to a health-enhancing lifestyle; this was somewhat more common for women than men. Expectant parents with normal body mass index and vigorous physical activity were more likely to have very good or excellent self-rated health. Conclusions: Most expectant parents perceived their general health as good, although this perception was less for women than men. Being overweight and having a non-health-enhancing lifestyle were more common for men than women. Thus, there is need for more powerful health-promoting interventions for expectant parents.

  • 111.
    Fahlén, Jessica
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Essays on spatial point processes and bioinformatics2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis consists of two separate parts. The first part consists of one paper and considers problems concerning spatial point processes and the second part includes three papers in the field of bioinformatics.

    The first part of the thesis is based on a forestry problem of estimating the number of trees in a region by using the information in an aerial photo, showing the area covered by the trees. The positions of the trees are assumed to follow either a binomial point process or a hard-core Strauss process. Furthermore, discs of equal size are used to represent the tree-crowns. We provide formulas for the expectation and the variance of the relative vacancy for both processes. The formulas are approximate for the hard-core Strauss process. Simulations indicate that the approximations are accurate. 

    The second part of this thesis focuses on pre-processing of microarray data. The microarray technology can be used to measure the expression of thousands of genes simultaneously in a single experiment. The technique is used to identify genes that are differentially expressed between two populations, e.g. diseased versus healthy individuals. This information can be used in several different ways, for example as diagnostic tools and in drug discovery.

    The microarray technique involves a number of complex experimental steps, where each step introduces variability in the data. Pre-processing aims to reduce this variation and is a crucial part of the data analysis. Paper II gives a review over several pre-processing methods. Spike-in data are used to describe how the different methods affect the sensitivity and bias of the experi­ment.

    An important step in pre-processing is dye-normalization. This normalization aims to re­move the systematic differences due to the use of different dyes for coloring the samples. In Paper III a novel dye-normalization, the MC-normalization, is proposed. The idea behind this normaliza­tion is to let the channels’ individual intensities determine the cor­rection, rather than the aver­age intensity which is the case for the commonly used MA-normali­zation. Spike-in data showed that  the MC-normalization reduced the bias for the differentially expressed genes compared to the MA-normalization.

    The standard method for preserving patient samples for diagnostic purposes is fixation in formalin followed by embedding in paraffin (FFPE). In Paper IV we used tongue-cancer micro­RNA-microarray data to study the effect of FFPE-storage. We suggest that the microRNAs are not equally affected by the storage time and propose a novel procedure to remove this bias. The procedure improves the ability of the analysis to detect differentially expressed microRNAs.

  • 112.
    Fahlén, Jessica
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Landfors, Mattias
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Freyhult, Eva
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology. Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Bylesjö, Max
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hvidsten, Torgeir
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Rydén, Patrik
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Bioinformatics strategies for cDNA-microarray data processing2009In: Batch effects and noise in microarray experiments: sources and solutions / [ed] Scherer, Andreas, Wiley and Sons , 2009, 1, , p. 272p. 61-74Chapter in book (Other academic)
    Abstract [en]

    

    Pre-processing plays a vital role in cDNA-microarray data analysis. Without proper pre-processing it is likely that the biological conclusions will be misleading. However, there are many alternatives and in order to choose a proper pre-processing procedure it is necessary to understand the effect of different methods. This chapter discusses several pre-processing steps, including image analysis, background correction, normalization, and filtering. Spike-in data are used to illustrate how different procedures affect the analytical ability to detect differentially expressed genes and estimate their regulation. The result shows that pre-processing has a major impact on both the experiment’s sensitivity andits bias. However, general recommendations are hard to give, since pre-processing consists of several actions that are highly dependent on each other. Furthermore, it is likely that pre-processing have a major impact on downstream analysis, such as clustering and classification, and pre-processing methods should be developed and evaluated with this in mind.

  • 113.
    Fahlén, Jessica
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Rentoft, Matilda
    Umeå University, Faculty of Medicine, Department of Medical Biosciences.
    Rydén, Patrik
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    MicroRNA-microarray data analysis in the precence of FFPE storage time effects2010Manuscript (preprint) (Other academic)
    Abstract [en]

    Background: The standard method for preserving patient samples for diagnostic purposes is fixation in formalin followed by embedding in paraffin (FFPE). The use of FFPE blocks makes it possible to include a large number of patients in the experimental studies since millions of FFPE blocks are stored around the world. However, FFPE storage can cause degradation and modifi­cations of nucleic acids. In order to draw reliable biological conclusions it is therefore important to know what effect FFPE-storage have on the tissues and to have procedures that normalize this effect. In this paper, we study the effect that FFPE-storage has on microRNA-microarray data from tongue-cancer patients and propose a novel procedure for normalizing the bias intro­duced by FFPE-storage.

    Results: MicroRNA-microarray data from 21 tongue-cancer patients and 8 control patients were used. The samples were stored in FFPE blocks and had been in storage for up to 11 years. The data contained a large amount of biological relevant variation, yet the largest variation was due to the samples storage times. The storage effect was shown to be significant and some results suggested that it may be causal. Moreover, the microRNAs were unequally affected by storage and this could partially be explained by sequence characteristics. The novel normaliza­tion procedure was shown to have a large impact in the analysis ability to identify differentially expressed microRNAs between young and old cancer patients as well as between cancer and control patients. The p-values for the top microRNAs candidates were much lower for the pro­posed novel normalization compared to a standard normalization procedure which suggested that the novel normalization made the analysis more efficient.

    Conclusions: MicroRNA-microarray data can be seriously affected by FFPE-storage and the introduced variation cannot be removed by standard normalizations. The proposed normaliza­tion removes the bias introduced by FFPE-storage and gives higher sensitivity than the standard normalization.

  • 114.
    Ferm, Martin
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Prediktering av skogliga variabler med data från flygburen laser: En jämförelse mellan multipla regressionsmodeller och k nearest neighbour-modeller2010Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 115.
    Fowler, Philip
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Lindblad, Pernilla
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    The Minimum Description Length principle in model selection: An evaluation of the renormalized maximum likelihood criterion in linear- and logistic regression analysis2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 116.
    Freij, Lennart
    et al.
    Umeå University, Faculty of Social Sciences, Statistics.
    Wall, Stig
    Umeå University, Faculty of Social Sciences, Statistics.
    Exploring Child Health and its Ecology1977Doctoral thesis, monograph (Other academic)
  • 117.
    Freyhult, Eva
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    Landfors, Mattias
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology. Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Önskog, Jenny
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Hvidsten, Torgeir R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Rydén, Patrik
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Umeå University, Faculty of Social Sciences, Department of Statistics.
    Challenges in microarray class discovery: a comprehensive examination of normalization, gene selection and clustering2010In: BMC Bioinformatics, ISSN 1471-2105, E-ISSN 1471-2105, Vol. 11, article id 503Article in journal (Refereed)
    Abstract [en]

    Background: Cluster analysis, and in particular hierarchical clustering, is widely used to extract information from gene expression data. The aim is to discover new classes, or sub-classes, of either individuals or genes. Performing a cluster analysis commonly involve decisions on how to; handle missing values, standardize the data and select genes. In addition, pre processing, involving various types of filtration and normalization procedures, can have an effect on the ability to discover biologically relevant classes. Here we consider cluster analysis in a broad sense and perform a comprehensive evaluation that covers several aspects of cluster analyses, including normalization.

    Result: We evaluated 2780 cluster analysis methods on seven publicly available 2-channel microarray data sets with common reference designs. Each cluster analysis method differed in data normalization (5 normalizations were considered), missing value imputation (2), standardization of data (2), gene selection (19) or clustering method (11). The cluster analyses are evaluated using known classes, such as cancer types, and the adjusted Rand index. The performances of the different analyses vary between the data sets and it is difficult to give general recommendations. However, normalization, gene selection and clustering method are all variables that have a significant impact on the performance. In particular, gene selection is important and it is generally necessary to include a relatively large number of genes in order to get good performance. Selecting genes with high standard deviation or using principal component analysis are shown to be the preferred gene selection methods. Hierarchical clustering using Ward's method, k-means clustering and Mclust are the clustering methods considered in this paper that achieves the highest adjusted Rand. Normalization can have a significant positive impact on the ability to cluster individuals, and there are indications that background correction is preferable, in particular if the gene selection is successful. However, this is an area that needs to be studied further in order to draw any general conclusions.

    Conclusions: The choice of cluster analysis, and in particular gene selection, has a large impact on the ability to cluster individuals correctly based on expression profiles. Normalization has a positive effect, but the relative performance of different normalizations is an area that needs more research. In summary, although clustering, gene selection and normalization are considered standard methods in bioinformatics, our comprehensive analysis shows that selecting the right methods, and the right combinations of methods, is far from trivial and that much is still unexplored in what is considered to be the most basic analysis of genomic data.

  • 118.
    Gustafsson, Lennart
    Umeå University, Faculty of Social Sciences, Statistics.
    Några aspekter på stickprovsteorier vid ändliga populationer med tillämpningar på tvåstegsurval1968Licentiate thesis, monograph (Other academic)
  • 119.
    Gustavsson, André
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Elpriserna på den nordiska elbörsen: Prognosmodellering med hjälp av ARIMA-modeller2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 120.
    Gustavsson, André
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Prognossäkerhet: Tillför en heteroskedastisk modell någon säkerhet hos Box och Jenkins prognosmodeller?2010Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 121.
    Gärling, Tommy
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business.
    Laitila, Thomas
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Marell, Agneta
    Umeå University, Faculty of Social Sciences, Umeå School of Business.
    Westin, Kerstin
    Umeå University, Faculty of Social Sciences, Department of Social and Economic Geography.
    A note on the short term effects of deregulation of the Swedish Taxicab Industry1995In: Journal of Transport Economics and Policy, ISSN 0022-5258, E-ISSN 1754-5951, Vol. 29, no 2, p. 209-214Article in journal (Refereed)
  • 122.
    Gärling, Tommy
    et al.
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Laitila, Thomas
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Marell, Agneta
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE).
    Westin, Kerstin
    Umeå University, Faculty of Social Sciences, Department of Social and Economic Geography.
    Avreglering av taxi i Sverige1993Report (Other academic)
  • 123.
    Gärling, Tommy
    et al.
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Laitila, ThomasUmeå University, Faculty of Social Sciences, Department of Statistics.Westin, KerstinUmeå University, Faculty of Social Sciences, Department of Geography and Economic History.
    Theoretical foundations for travel choice modeling1998Collection (editor) (Refereed)
  • 124.
    Haugen, Katarina
    et al.
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Holm, Einar
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Häggström Lundevaller, Erling
    Umeå University, Faculty of Social Sciences, Social and Economic Geography. Statistics.
    Westin, Kerstin
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Friska, småkrassliga och sjuka2006In: Sjukförsäkring, kulturer och attityder - Fyra aktörers perspektiv, Försäkringskassan , 2006Chapter in book (Refereed)
  • 125.
    Haugen, Katarina
    et al.
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Holm, Einar
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Häggström Lundevaller, Erling
    Statistics. Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Westin, Kerstin
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Individer, attityder och ohälsa2006In: Sjukförsäkring, kulturer och attityder - Fyra aktörers perspektiv, Försäkringskassan , 2006Chapter in book (Refereed)
  • 126.
    Haugen, Katarina
    et al.
    Umeå University, Faculty of Social Sciences, Department of Social and Economic Geography.
    Holm, Einar
    Umeå University, Faculty of Social Sciences, Department of Social and Economic Geography.
    Häggström Lundevaller, Erling
    Umeå University, Faculty of Social Sciences, Department of Statistics. Umeå University, Faculty of Social Sciences, Department of Social and Economic Geography.
    Westin, Kerstin
    Umeå University, Faculty of Social Sciences, Department of Social and Economic Geography.
    Localised attitudes matter: a study of sickness absence in Sweden2008In: Population, Space and Place, ISSN 1544-8444, E-ISSN 1544-8452, Vol. 14, no 3, p. 189-207Article in journal (Refereed)
    Abstract [en]

    The central issues explored in this article are the importance of geographical location in explaining the attitudes of individuals, and the interplay between these attitudes and overt behaviour. The context is as follows: In the late 1990's, sick-listings in Sweden underwent a substantial increase, causing the public expenses for the general sickness insurance to soar. Moreover, the extent of the usage of the insurance was found to vary significantly across different regions within the country. This development of the sickness insurance generally, and the regional differences specifically, have since been the subject of an intense debate. Differences and/or changes in attitudes toward sick leave within the population have been proposed as possible reasons for the regional variations. Much of the discussion has, however, been based on speculative arguments rather than empirical studies. Using data from a survey conducted in 2005, this research explores whether geographical location influences individual attitudes toward sick leave, and whether these attitudes in turn influence the sickness absence of individuals. The data are analysed using factor analysis, ordinary linear regressions and logistic regressions. The results provide some support for the idea that geographical factors matter to individual attitudes, and that variation in these attitudes is in turn associated with propensity for sickness absence. Copyright © 2008 John Wiley & Sons, Ltd.

  • 127.
    Henriksson, Widar
    et al.
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    Stenlund, TovaUmeå University, Faculty of Social Sciences, Department of Educational Measurement.Sundström, AnnaUmeå University, Faculty of Social Sciences, Department of Educational Measurement.Wiberg, MarieUmeå University, Faculty of Social Sciences, Department of Educational Measurement. Umeå University, Faculty of Social Sciences, Department of Statistics.
    Proceedings from the conference: The GDE-model as a guide in driver training and testing: Umeå, May 7-8, 20072007Conference proceedings (editor) (Other (popular science, discussion, etc.))
  • 128.
    Henriksson, Widar
    et al.
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    Stenlund, Tova
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    Sundström, Anna
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    Wiberg, Marie
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement. Umeå University, Faculty of Social Sciences, Department of Statistics.
    The GDE-model as a guide in driver training and testing.: Proceedings from the conference, Umeå, May 7-8, 20072007Report (Other academic)
  • 129.
    Henriksson, Widar
    et al.
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    Sundström, Anna
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    Wiberg, Marie
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement. Umeå University, Faculty of Social Sciences, Department of Statistics.
    The Swedish driving-license test: A summary of studies from the department of educational measurement2004Report (Other academic)
    Abstract [en]

    Since 1990, the Department of Educational Measurement at Umeå University has been commissioned to study the Swedish drivinglicense test by the Swedish National Road Administration, SNRA. Over the past few years several studies have been conducted in order to develop and improve the Swedish driving-license test. The focus of the majority of the studies has been the theory test.

    The aims of this paper were threefold: firstly to describe the development of the driver education and the driving-license test in Sweden during the past century; secondly, to summarize the findings of our research, which is related to important issues in test development; and finally, to make some suggestions for further research.

  • 130.
    Hietala, Sven-Ola
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Social Sciences, Department of Statistics.
    Segerstedt, Bo
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Social Sciences, Department of Statistics.
    Wirell, S
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Social Sciences, Department of Statistics.
    Sunnegårdh, O
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Social Sciences, Department of Statistics.
    Östberg, P
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Social Sciences, Department of Statistics.
    Östh, L
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Social Sciences, Department of Statistics.
    Effects of contrast media on renal graft function and survival after cerebral angiography of cadaveric donors1989In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 30, no 3, p. 317-319Article in journal (Refereed)
    Abstract [en]

    The effects of intravascularly administered ionic contrast media on renal graft function and survival were retrospectively evaluated in 211 recipients of cadaveric renal transplants. The renal grafts were explanted from the donors within 24 hours (mean 16 hours) after cerebral angiography. There were no differences in renal function or graft survival between those exposed and those not exposed to contrast media before nephrectomy.

  • 131.
    Holm, Einar
    et al.
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Lindgren, Urban
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Eriksson, Madeleine
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Eriksson, Rikard
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Häggström Lundevaller, Erling
    Statistics. Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Holme, Kirsten
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Strömgren, Magnus
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Transfereringar och arbete2004Report (Other academic)
  • 132.
    Holm, Einar
    et al.
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Lindgren, Urban
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Häggström Lundevaller, Erling
    Statistics. Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Strömgren, Magnus
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    SVERIGE2007In: Modelling our Future: Population Ageing, Health and Aged Care, Elsevier, Amsterdam , 2007, p. 543-549Chapter in book (Refereed)
  • 133.
    Holm, Einar
    et al.
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Lindgren, Urban
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Häggström Lundevaller, Erling
    Statistics. Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    Strömgren, Magnus
    Umeå University, Faculty of Social Sciences, Social and Economic Geography.
    The SVERIGE spatial micro simulation model2006In: 8th Nordic Seminar on Microsimulation Models, 2006Conference paper (Other academic)
  • 134.
    Holmberg, Henrik
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Generalised linear models with clustered data2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In situations where a large data set is partitioned into many relativelysmall clusters, and where the members within a cluster have some common unmeasured characteristics, the number of parameters requiring estimation tends to increase with sample size if a fixed effects model is applied. This fact causes the assumptions underlying asymptotic results to be violated. The first paper in this thesis considers two possible solutions to this problem, a random intercepts model and a fixed effects model, where asymptoticsare replaced by a simple form of bootstrapping. A profiling approach is introduced in the fixed effects case, which makes it computationally efficient even with a huge number of clusters. The grouping effect is mainly seen as a nuisance in this paper.

    In the second paper the effect of misspecifying the distribution of the random effects in a generalised linear mixed model for binary data is studied. One problem with mixed effects models is that the distributional assumptions about the random effects are not easily checked from real data. Models with Gaussian, logistic and Cauchy distributional assumptions are used for parameter estimation on data simulated using the same three distributions. The effect of these assumptions on parameter estimation is presented. Two criteria for model selection are investigated, the Akaike information criterion and a criterion based on a chi-square statistic. The estimators for fixed effects parameters are quite robust against misspecification of the random effects distribution, at least with the distributions used in this paper. Even when the true random effects distribution is Cauchy, models assuming a Gaussian or a logistic distribution regularly produce estimates with less bias.

  • 135.
    Holmberg, Henrik
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Generalised linear models with clustered data: robustness against a misspecified random effects distributionManuscript (preprint) (Other academic)
  • 136.
    Holmberg, Henrik
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE).
    Broström, Göran
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    On statistical methods for clustering: a case study on infant mortality, northern Sweden 1831-1890Manuscript (preprint) (Other academic)
  • 137.
    Holmström, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Oudin, Anna
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Nilsson, Karina
    Umeå University, Faculty of Social Sciences, Department of Sociology.
    Lindgren, Urban
    Umeå University, Faculty of Social Sciences, Department of Social and Economic Geography.
    Bergdahl, Ingvar
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
    Ivarsson, Anneli
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    SIMSAM-nätverket i Umeå strävar mot att bli ett framstående center för registerforskning som knyter samman barndomen med livslång hälsa och välfärd2011In: SVEPET - Medlemstidning för Svensk Epidemiologisk Förening (SVEP), ISSN 1101-4385, Vol. 29, no 3, p. 8-9Article in journal (Other academic)
    Abstract [sv]

    Vetenskapsrådets SIMSAM initiativ syftar till att stärka multidisciplinär registerforskning i Sverige. Inom SIMSAM-nätverket i Umeå arbetar vi tvärvetenskapligt med sikte på att utvecklas till ett center med excellens kring mikrodataforskning som knyter samman barndomen med livslång hälsa och välfärd. Just nu fokuserar vi på att få tillgång till sammanlänkade data från ett flertal nationella och regionala register för att komma vidare med vår planerade forskning. Dessutom har Umeå-nätverket nyligen fått i uppdrag att leda den nationella samordningen av SIMSAM initiativet.

  • 138.
    Hägg, David
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Olsson, Henrik
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Komorbida sjukdomar hos individer med svår psoriasis: En analys med logistiska och loglinjära modeller2010Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 139.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Bandwidth selection for backfitting estimation of semiparametric additive modelsManuscript (preprint) (Other academic)
  • 140.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Selection of smoothing parameters with application in causal inference2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is a contribution to the research area concerned with selection of smoothing parameters in the framework of nonparametric and semiparametric regression. Selection of smoothing parameters is one of the most important issues in this framework and the choice can heavily influence subsequent results. A nonparametric or semiparametric approach is often desirable when large datasets are available since this allow us to make fewer and weaker assumptions as opposed to what is needed in a parametric approach. In the first paper we consider smoothing parameter selection in nonparametric regression when the purpose is to accurately predict future or unobserved data. We study the use of accumulated prediction errors and make comparisons to leave-one-out cross-validation which is widely used by practitioners. In the second paper a general semiparametric additive model is considered and the focus is on selection of smoothing parameters when optimal estimation of some specific parameter is of interest. We introduce a double smoothing estimator of a mean squared error and propose to select smoothing parameters by minimizing this estimator. Our approach is compared with existing methods.The third paper is concerned with the selection of smoothing parameters optimal for estimating average treatment effects defined within the potential outcome framework. For this estimation problem we propose double smoothing methods similar to the method proposed in the second paper. Theoretical properties of the proposed methods are derived and comparisons with existing methods are made by simulations.In the last paper we apply our results from the third paper by using a double smoothing method for selecting smoothing parameters when estimating average treatment effects on the treated. We estimate the effect on BMI of divorcing in middle age. Rich data on socioeconomic conditions, health and lifestyle from Swedish longitudinal registers is used.

  • 141.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Data-driven smoothing parameter selection for estimating average treatment effectsManuscript (preprint) (Other academic)
  • 142.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Estimating prediction error: cross-validation vs. accumulated prediction error2010In: Communications in statistics. Simulation and computation, ISSN 0361-0918, E-ISSN 1532-4141, Vol. 39, no 5, p. 880-898Article in journal (Refereed)
    Abstract [en]

    We study the validation of prediction rules such as regression models and classification algorithms through two out-of-sample strategies, cross-validation and accumulated prediction error. We use the framework of Efron (1983) where measures of prediction errors are defined as sample averages of expected errors and show through exact finite sample calculations that cross-validation and accumulated prediction error yield different smoothing parameter choices in nonparametric regression. The difference in choice does not vanish as sample size increases.

  • 143.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Westerlund, Olle
    Umeå University, Faculty of Social Sciences, Department of Economics.
    Norberg, Margareta
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Divorcing in middle age and its effects on BMIManuscript (preprint) (Other academic)
  • 144.
    Häggström, Jonas
    Umeå University, Faculty of Social Sciences, Statistics.
    The Minimax Approach to Optimum Design of Experiments2000Doctoral thesis, monograph (Other academic)
  • 145.
    Häggström lundevaller, Erling
    Umeå University, Faculty of Social Sciences, Statistics.
    A comparison between bootstrap methods for generalized linear models1996In: Proceedings of the forth Umeå Wurzburg conference in statistics, 1996Conference paper (Other academic)
  • 146.
    Häggström Lundevaller, Erling
    Umeå University, Faculty of Social Sciences, Statistics.
    A frequency model for shopping and recreational trips in Sweden2002Report (Other academic)
    Abstract [en]

    In this article a trip frequency model for recreational and shopping

    trips is suggested. The data used comes from a Swedish travel habit

    survey where the observations of trip frequencies of both types on each

    individual are made on the same day. This is likely to introduce a correlation

    structure, which is modeled with a conditional approach where

    the number of recreational trips are assumed to be made conditional

    on the number of shopping trips. A special interest is devoted to the

    effect of travel cost on trip frequencies. As a measure of the sensitivity

    of cost changes, elasticity of demand is calculated. The precision of

    the elasticities are evaluated with simulated confidence intervals.

  • 147.
    Häggström Lundevaller, Erling
    Umeå University, Faculty of Social Sciences, Statistics. Social and Economic Geography.
    Demografisk mikrosimulering2007In: Qvartilen, ISSN 0283-3654, Vol. 22, no 3Article in journal (Other (popular science, discussion, etc.))
  • 148.
    Häggström Lundevaller, Erling
    Umeå University, Faculty of Social Sciences, Statistics.
    Measurement errors in Poisson regressions: A simulation study based on travel frequency data2006In: Journal of Transportation and Statistics, vol 9, Nr 1 ., ISSN 1094-8848, Vol. 9, no 1, p. 39-48Article in journal (Refereed)
    Abstract [en]

    This paper considers how measurement errors in the explanatory

    variables affects the analysis of a Poisson regression model for frequencies

    of recreational and shopping trips. Measurement errors can introduce

    bias in the parameter estimates and the effects on this particular

    data set and model is investigated. The structure of the data, with two

    observations on each individual, makes it desirable to test for correlation

    within individual. It is possible that tests of random effects are

    sensitive to measurement error. The properties of tests of random individual

    effects when there are measurement errors are therefore studied

    in the paper. The results of a simulation study show that classical

    measurement errors cause severe bias and Berkson measurement errors

    produce little bias. The tests for random individual effects work

    well both with measurement error and negatively correlated responses

    according to the simulation study.

  • 149.
    Häggström Lundevaller, Erling
    Umeå University, Faculty of Social Sciences, Statistics. Social and Economic Geography.
    Prognostisering och simulering av turistresor i Sverige: Med fokus på den framtida skidturismen2008Report (Other academic)
  • 150.
    Häggström Lundevaller, Erling
    Umeå University, Faculty of Social Sciences, Statistics.
    Properties of Honda's test of random individual effects in non-linear regression.2002In: Statistical papers, ISSN 0932-5026, Vol. 43, p. 177-196Article in journal (Refereed)
1234567 101 - 150 of 303
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