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  • 201.
    Lundquist, Kristina
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    A comparative study of Stochastic and Deterministic Population Models2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 202.
    Löfgren, Kent
    et al.
    Umeå University, Faculty of Social Sciences, Educational Measurement.
    Törnkvist, Birgitta
    Statistics.
    Jämförelser mellan studerande i olika antagningsgrupper som har registrerats på ekonomprogram2004Report (Other academic)
    Abstract [sv]

    This study was about students and their study achievements. Data from available records for students admitted to the study programme of business administration was used. The students (N19393) were born in the period 1972–1984, living in Sweden and registered on the study programme sometime between 1993 and 2000. The students were divided into three groups on the basis of the grounds on which the students had been admitted. The first group had been admitted on the basis of their credits from uppersecondary school, the second on the basis of their SweSAT-scores and the third group on the basis of their SweSAT-scores with additional credit for work experience. Study achievement was defined as the number of credits the students managed to attain each semester. The purpose of the study was to see if there were any differences in academic achievement between the three groups. Attention was also given to social background and sex. The results showed that approximately 50% of the students were women. The proportion of students from Social Group 1 was highest among those who had been admitted on the basis of their SweSAT-scores. The most common upper-secondary school programme, for the students who had completed upper-secondary school 1997 or later, was the Programme for Social Science (Samhällsvetenskaplig utbildning). About one fifth of the students who had completed upper secondary school 1997-1999 had taken supplementary secondary-education-level courses after they had left upper-secondary school. The study showed that the female students attained more course points per semester than the male students. There were also differences, in terms of the number of credits attained per term, between the students from the three groups and between students with different social backgrounds. However, these differences were not as extensive as the differences between male and female study achievements.

  • 203.
    Löfgren, Kent
    et al.
    Umeå University, Faculty of Social Sciences, Educational Measurement.
    Törnkvist, Birgitta
    Statistics.
    Jämförelser mellan studerande i olika antagningsgrupper som har registrerats på socionomprogrammet2004Report (Other academic)
    Abstract [sv]

    Students and their study achievements are in focus in this report. Attention is given to the three and a half year long Programme for Social Work. The students (N2956) where divided into three groups, according to the grounds on which they had been admitted to the programme. The first group had been admitted on the basis of their credits from upper-secondary school, the second on the basis of their SweSAT-scores and the third group on the basis of their SweSAT-scores with additional credit for work experience. The purpose of the study was to see if there were any differences in academic achievement between the three groups. Academic achievement was defined as the number of credits achieved at university. Attention was also given to social backgrounds and male/female variance. The results showed that approximately 85% of the students were women. The proportion of students from Social Group 1 was highest among those who had been admitted on the basis of their credits from upper-secondary school. The most common uppersecondary school programme was the Programme for Social Science (Samhällsvetenskaplig utbildning). About one fourth of the students who had completed upper-secondary school 1997-1999 had taken supplementary secondary education level courses after they had left upper-secondary school. The study showed that the female students attained more course points per

    term compared to the male students. There were also differences, in terms of the number of credits attained per term, between the students from the three groups and between students with different socio-economic backgrounds. However, these differences were not as extensive as the differences between male and female study achievements.

  • 204.
    Malmdin, Joakim
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Interval censored status change in survival analysis, an EM approachManuscript (preprint) (Other academic)
  • 205.
    Malmdin, Joakim
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Interval censored time of status change in survival analysis2009Licentiate thesis, comprehensive summary (Other academic)
  • 206.
    Malmdin, Joakim
    et al.
    Umeå University, Faculty of Social Sciences, Statistics.
    Broström, Göran
    Umeå University, Faculty of Social Sciences, Statistics.
    Interval Censored Status Changes in Survival Analysis2007In: ISI 2007 Book of Abstracts: 56th Session of the International Statistical Institute 22-29 August 2007 Lisboa, Portugal, 2007, p. 1-Conference paper (Other academic)
  • 207.
    Malmdin, Joakim
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Göran, Broström
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Interval censored status change in survival analysis using Cox regressionManuscript (preprint) (Other academic)
  • 208.
    Malmdin, Joakim
    et al.
    Umeå University, Faculty of Social Sciences, Statistics.
    Olofsson, Jens
    Ledare Qvartilen 22-12007Other (Other (popular science, discussion, etc.))
  • 209.
    Malmdin, Joakim
    et al.
    Umeå University, Faculty of Social Sciences, Statistics.
    Olofsson, Jens
    Ledare Qvartilen 22-22007Other (Other (popular science, discussion, etc.))
  • 210.
    Malmdin, Joakim
    et al.
    Umeå University, Faculty of Social Sciences, Statistics.
    Olofsson, Jens
    Ledare Qvartilen 22-32007Other (Other (popular science, discussion, etc.))
  • 211.
    Malmdin, Joakim
    et al.
    Umeå University, Faculty of Social Sciences, Statistics.
    Olofsson, Jens
    Ledare Qvartilen 22-42007Other (Other (popular science, discussion, etc.))
  • 212.
    Marell, Agneta
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business.
    Davidsson, Per
    Gärling, Tommy
    Umeå University, Faculty of Social Sciences, Umeå School of Business.
    Laitila, Thomas
    Statistics.
    Direct and indirect effects on households' intentions to replace the old car2004In: Journal of Retailing and Consumer Services, ISSN 0969-6989, Vol. 11, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    With the purpose of testing the hypothesis that households' intentions to replace their old car have a direct negative relationship to its perceived quality ('current level') and a direct positive relationship to their aspirations for a new car ('aspiration level'), a rotating panel of car owners were interviewed every fourth month during 2 years. In this data set the hypothesis received support. In addition the results showed that the age of the car, the total number of miles driven, and the number of anticipated repairs affected the current level, whereas marital status, the number of children, consumer confidence, and environmental concern affected the aspiration level.

  • 213.
    Moritz, Elin
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Skattning av kausala effekter vid effektmodifiering genom matchning på funktioner av prognostic scores2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 214.
    Möller, Christian
    et al.
    Umeå University, Faculty of Medicine, Clinical Sciences, Otorhinolaryngology. Umeå University, Faculty of Medicine, Clinical Sciences, Paediatrics.
    Broström, Göran
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    A new method to relate symptom scores with pollen counts, A dynamic model for comparison of treatments of allergy1989In: Grana, ISSN 0017-3134, E-ISSN 1651-2049, Vol. 14, p. 113-123Article in journal (Refereed)
  • 215.
    Möllsten, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Paediatrics.
    Svensson, Maria
    Department of Nephrology, Sahlgrenska University Hospital, Gothenburg, Sweden.
    Waernbaum, Ingeborg
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Berhan, Yonas
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Paediatrics.
    Schön, Staffan
    Department of Internal Medicine, Ryhov County Hospital, Jönköping, Sweden.
    Nyström, Lennarth
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Arnqvist, Hans J.
    Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
    Dahlquist, Gisela
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Paediatrics.
    Cumulative risk, age at onset, and sex-specific differences for developing end-stage renal disease in young patients with type 1 diabetes: A nationwide population-based cohort study2010In: Diabetes, ISSN 0012-1797, E-ISSN 1939-327X, Vol. 59, no 7, p. 1803-1808Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE—This study aimed to estimate the current cumulativerisk of end-stage renal disease (ESRD) due to diabeticnephropathy in a large, nationwide, population-based prospectivetype 1 diabetes cohort and specifically study the effects ofsex and age at onset.RESEARCH DESIGN AND METHODS—In Sweden, all incidentcases of type 1 diabetes aged 0–14 years and 15–34 years arerecorded in validated research registers since 1977 and 1983,respectively. These registers were linked to the Swedish RenalRegistry, which, since 1991, collects data on patients who receiveactive uremia treatment. Patients with 13 years duration of type1 diabetes were included (n 11,681).RESULTS—During a median time of follow-up of 20 years, 127patients had developed ESRD due to diabetic nephropathy. Thecumulative incidence at 30 years of type 1 diabetes duration waslow, with a male predominance (4.1% [95% CI 3.1–5.3] vs. 2.5%[1.7–3.5]). In both male and female subjects, onset of type 1diabetes before 10 years of age was associated with the lowestrisk of developing ESRD. The highest risk of ESRD was found inmale subjects diagnosed at age 20–34 years (hazard ratio 3.0 [95%CI 1.5–5.7]). In female subjects with onset at age 20–34 years, therisk was similar to patients’ diagnosed before age 10 years.CONCLUSIONS—The cumulative incidence of ESRD is exceptionallylow in young type 1 diabetic patients in Sweden. There isa striking difference in risk for male compared with femalepatients. The different patterns of risk by age at onset and sexsuggest a role for puberty and sex hormones.

  • 216.
    Nanos, Nikos
    et al.
    Technical University of Madrid, Spain.
    Larson, Kajsa
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Milleron, Matias
    Technical University of Madrid, Spain.
    Sjöstedt de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Inverse modeling for effective dispersal: Do we need tree size to estimate fecundity?2010In: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 221, no 20, p. 2415-2424Article in journal (Refereed)
    Abstract [en]

    The estimation of the dispersal kernel for the seedling and sapling stages of the recruitment process was made possible through the application of inverse modeling to dispersal data. This method uses the spatial coordinates of adult trees and the counts of seedlings (or saplings) in small quadrats to estimate the dispersal kernel. The unknown number of recruits produced by an adult tree (the fecundity) is estimated – simultaneously with the dispersal kernel – via an allometric linear model relating the unknown quantity with a (easily) measured characteristic of the adult tree (usually the basal area). However, the allometric relation between tree size and reproductive success in the sapling (or seedling) stage may not be strong enough when numerous, well-documented, post-dispersal processes (such as safe-site limitation for recruitment) cause large post-dispersal seedling mortality, which is usually unrelated to the size of the tree that dispersed them. In this paper we hypothesize that when tree size and reproductive success in the seedling/sapling stage are not well correlated then the use of allometry in inverse modeling is counter-productive and may lead to poor model fits. For these special cases we suggest using a new model for effective dispersal that we term the unrestricted fecundity (UF) model that, contrary to allometric models, makes no assumptions on the fecundities; instead they are allowed to vary freely from one tree to another and even to be zero for trees that are reproductively inactive. Based on this model, we examine the hypothesis that when tree size and reproductive success are weakly correlated and the fecundities are estimated independently of tree size the goodness-of-fit and the ecological meaning of dispersal models (in the seedling or sapling stage) may be enhanced. Parameters of the UF model are estimated through the EM algorithm and their standard errors are approximated via the observed information matrix. We fit the UF model to a dataset from an expanding European beech population of central Spain as well as to a set of simulated dispersal data were the correlation between reproductive success and tree size was moderate. In comparisons with a simple allometric model, the UF model fitted the data better and the parameter estimates were less biased. We suggest using this new approach for modeling dispersal in the seedling and sapling stages when tree size (or other adult-specific covariates) is not deemed to be in strong relation to the reproductive success of adults. Models that use covariates for modeling the fecundity of adults should be preferred when reproductive success and tree size guard a strong relationship.

  • 217.
    Norberg, Margareta
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health. 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 Statistics.
    Ng, Nawi
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health. Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).
    Broström, Göran
    Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS). Umeå University, Faculty of Social Sciences, Department of Social and Economic Geography.
    Who is using snus? - Time trends, socioeconomic and geographic characteristics of snus users in the ageing Swedish population2011In: BMC Public Health, ISSN 1471-2458, E-ISSN 1471-2458, Vol. 11, p. 929-Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The prevalence of smoking in Sweden has decreased in recent decades, and is now among the lowest in the world. During the same period, the use of Swedish moist oral snuff, a smokeless tobacco called snus, has increased. Few studies have evaluated time trends of the socioeconomic and geographic characteristics of snus users in Sweden. This paper contributes to filling that gap.

    METHODS: This study utilized the Linnaeus Database, which links national registers with comprehensive individual data on socioeconomic status (SES) to health data from a large ongoing health survey, the Västerbotten Intervention Programme (VIP). The VIP targets the entire middle-aged population of Västerbotten county at ages 40, 50 and 60 years with yearly cross-sectional surveys including self-reported data on tobacco habits. Time trends of snus use among 92,563 VIP-participants across different areas of residence and smoking groups were investigated graphically. Logistic regression was performed to estimate the associations between SES and geographical variables and current use versus non-use of snus.

    RESULTS: Overall, in parallel to decreasing smoking, the increasing trend of snus use in this middle-aged population continues, particularly in 40-year-olds. In both genders, the highest prevalence of snus use was observed among previous smokers. The prevalence of snus use also increased over time among smokers, and was consistently higher compared to those who had never smoked. Among males - both those who had never smoked and previous smokers - low education (OR 1.21, 95%CI 1.06-1.40 and OR 1.28, 95%CI 1.14-1.43), living alone (OR 1.16, 95%CI 1.07-1.27 and OR 1.13, 95%ci 1.04-1.23), low income and living in rural areas was associated with using snus, while this was not seen among male current smokers. Among women, living alone was associated with using snus irrespective of smoking habits. Among female smokers, the OR for snus use increased with higher education.

    CONCLUSIONS: A disadvantaged social profile and also higher prevalence in rural areas is observed among male snus users who had never smoked or were previous smokers. Among male smokers there was no association between SES and use of snus. The prevalence of snus use among women is increasing, but is still considerably lower than that of men. The association between snus and SES characteristics is less pronounced among women, although snus is clearly linked to living alone. These patterns should be taken into consideration in tobacco control policies.

  • 218.
    Nyquist, Hans
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Recent Studies on Lp-Norm Estimation1980Doctoral thesis, monograph (Other academic)
    Abstract [en]

    When estimating the parameters in a linear regression model, the method of least squares (L^-norm estimator) is often used. When thè residuals are independent and identically normally distributed, the least squares estimator is BLUE as well as equivalent to the maximum likelihood estimator. However, the least squares estimator is known to be sensitive to departures from the assumption of normally distributed residuals. In a variety of applications there are theoretical as well as empirical evidences that the residuals display distributional properties different from those of normal distributions. It is therefore desirable to develop alternative estimators. Members of the class of Lp-norm estimators have here been proposed as alternatives to the least squares estimator.In this monograph, questions concerning the existence, uniqueness and asymptotic distributions of L^-norm estimators are discussed. It is seen that an L^-norm estimate will always exist and it will be u-nique for 1 < p < ». For p = 1 a necessary and sufficient condition on the regressors for unique estimation is given. The question of u-niqueness in large samples is also discussed. The asymptotic distribution of Lp-norm estimators i shown to be normal, for sufficiently small p. When selecting an L^-norm estimator, a procedure based on the asymptotic variance is proposed.Finally, the possibilities to construct L -norm based estimatorsPfor estimating multicollinear regression models and models with serially dependent residuals are discussed. L -norm based methods forPestimating interdependent systems are also considered.

  • 219.
    Okamoto, Sadahisa
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Hörnsten, Rolf
    Obayashi, Konen
    Wijayatunga, Priyantha
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Suhr, Ole B
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Continuous development of arrhythmia is observed in Swedish transplant patients with familial amyloidotic polyneuropathy (amyloidogenic transthyretin Val30Met variant)2011In: Liver transplantation, ISSN 1527-6465, E-ISSN 1527-6473, Vol. 17, no 2, p. 122-128Article in journal (Refereed)
    Abstract [en]

    In patients with familial amyloidotic polyneuropathy (FAP), heart complications are prognostic factors for mortality and morbidity after liver transplantation (LT). However, only a few studies have analyzed the development of arrhythmia in transplant patients with FAP. We investigated the development of arrhythmia requiring pacemaker insertion (PMI) in Swedish transplant patients with FAP, and we related the findings to gender, age at disease onset, and survival. One hundred four transplant patients with the amyloidogenic transthyretin Val30Met mutation were included in the study. Twenty-six (25%) received a pacemaker during the observation period (a median of 11 years after disease onset). This frequency was comparable to that noted in a previous study describing the natural course of FAP. No significant differences in PMI between early-onset cases (<50 years old) and late-onset cases (≥ 50 years old) or between genders were observed. PMI was not significantly related to patient survival. Our study confirms our previously reported short-time observation: LT does not prevent the development of heart arrhythmia necessitating PMI. The development of arrhythmia is unrelated to gender or age at disease onset, and the yearly risk does not appear to decrease with time after LT.

  • 220. Paulrud, Anton
    et al.
    Laitila, Thomas
    Umeå University, Faculty of Social Sciences, Statistics.
    Valuation of management policies for sport fishing on Sweden's Kaitum River2004In: Journal of Environmental Planning and Management, Vol. 42, p. 863-879Article in journal (Refereed)
  • 221. Paulrud, Anton
    et al.
    Laitila, Thomas
    Umeå University, Faculty of Social Sciences, Statistics.
    Valuation of management policies for sport-fishing on Sweden's Kaitum river2003Report (Other academic)
  • 222. Petrauskiene, V
    et al.
    Falk, M
    Waernbaum, Ingeborg
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Norberg, Margareta
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Public Health Sciences.
    Eriksson, Jan
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    The risk of venous thromboembolism is markedly elevated in patients with diabetes2005In: Diabetologia, Vol. 48, p. 1017–1021-Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To survey unnatural deaths among teenagers in northern Sweden and to suggest preventive measures. SETTING: The four northernmost counties (908,000 inhabitants, 1991), forming 55% of the area of Sweden. MATERIAL AND METHODS: All unnatural teenager deaths from 1981 through 2000 were identified in the databases of the Department of Forensic Medicine in Umea, National Board of Forensic Medicine. Police reports and autopsy findings were always studied, social and hospital records if present. RESULTS: Three hundred and fifty-five deaths were found, of which 267 (75%) were males and 88 (25%) females. Ninety out of 327 (28%) tested positive for alcohol. Two hundred and forty-eight (70%) were unintentional and 102 (30%) were intentional deaths, and five (1%) were categorized as undetermined manner of death. Unintentional deaths decreased while the incidence of intentional deaths remained unaffected by time. CONCLUSIONS: Injury-reducing measures have been effective concerning unintentional deaths and the fall in young licensed drivers due to the economical recess have probably also contributed to the decrease. However, there were no signs of decreasing numbers of suicides during the study period, which calls for resources to be allocated to suicide prevention.

  • 223.
    Pettersson, Hans
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Optimal design in average for inference in generalized linear models2005In: Statistical papers, ISSN 0932-5026, E-ISSN 1613-9798, Vol. 46, no 1, p. 79-100Article in journal (Refereed)
  • 224.
    Pettersson, Hans
    Umeå University, Faculty of Social Sciences, Statistics.
    Optimum in Average and Minimax Designs for Estimation of Generalized Linear Models2001Doctoral thesis, monograph (Other academic)
  • 225.
    Pettersson, Lennart
    et al.
    Umeå University, Faculty of Arts, History and Theory of Art.
    Wiberg, Marie
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Sålt och lottat: en studie av privatinköp och lotterier i Norrlands konstförening 1883 och 18842006Report (Other academic)
  • 226.
    Pettersson, Lennart
    et al.
    Umeå University, Faculty of Arts, History and Theory of Art.
    Wiberg, Marie
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Sålt och lottat: en studie av privatinköp och lotterier i Norrlands konstförening 1883 och 18842005Book (Other academic)
  • 227.
    Pollak, Kay
    Umeå University, Faculty of Social Sciences, Statistics.
    Variationsskattningar baserade på kvadratiska former av ordnade variabler: några illustrationer1969Licentiate thesis, monograph (Other academic)
  • 228.
    Pudas, Sara
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Persson, Jonas
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Josefsson, Maria
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Nilsson, Lars-Göran
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Brain Characteristics of Individuals Resisting Age-Related Cognitive Decline over Two Decades2013In: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 33, no 20, p. 8668-8677Article in journal (Refereed)
    Abstract [en]

    Some elderly appear to resist age-related decline in cognitive functions, but the neural correlates of successful cognitive aging are not well known. Here, older human participants from a longitudinal study were classified as successful or average relative to the mean attrition-corrected cognitive development across 15-20 years in a population-based sample (n = 1561). Fifty-one successful elderly and 51 age-matched average elderly (mean age: 68.8 years) underwent functional magnetic resonance imaging while performing an episodic memory face-name paired-associates task. Successful older participants had higher BOLD signal during encoding than average participants, notably in the bilateral PFC and the left hippocampus (HC). The HC activation of the average, but not the successful, older group was lower than that of a young reference group (n = 45, mean age: 35.3 years). HC activation was correlated with task performance, thus likely contributing to the superior memory performance of successful older participants. The frontal BOLD response pattern might reflect individual differences present from young age. Additional analyses confirmed that both the initial cognitive level and the slope of cognitive change across the longitudinal measurement period contributed to the observed group differences in BOLD signal. Further, the differences between the older groups could not be accounted for by differences in brain structure. The current results suggest that one mechanism behind successful cognitive aging might be preservation of HC function combined with a high frontal responsivity. These findings highlight sources for heterogeneity in cognitive aging and may hold useful information for cognitive intervention studies.

  • 229.
    Puu, Margareta
    Umeå University, Faculty of Social Sciences, Statistics.
    Optimum Experimental Designs for Generalized Linear Models with Multinomial Response2003Licentiate thesis, monograph (Other academic)
  • 230.
    Rentoft, Matilda
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Fahlén, Jessica
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Coates, PJ
    Laurell, Göran
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Otorhinolaryngology.
    Sjöström, Björn
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Otorhinolaryngology.
    Rydén, Patrik
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Nylander, Karin
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    miRNA analysis of formalin-fixed squamous cell carcinomas of the tongue is affected by age of the samples2011In: International Journal of Oncology, ISSN 1019-6439, Vol. 38, no 1, p. 61-69Article in journal (Refereed)
    Abstract [en]

    Global miRNA expression arrays were used for analysis of 836 miRNAs in formalin-fixed paraffin-embedded samples from 21 tongue cancer patients and 8 controls. Samples had been stored for one to eleven years. Results separated tumour samples from controls, however, the largest variation was correlated to sample storage time, detectable already after one year. With the use of a linear regression model we could adjust for the storage-dependent effect, leading to the identification of 54 differentially expressed miRNAs in tongue cancer, compared to 16 when using standard normalization, including up-regulation of a novel miRNA, miR-424.

  • 231.
    Sandström, Caroline
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Norling, Karl
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Female longevity: A survival analysis on 19th century women using the Cox Proportional Hazard model2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 232.
    Sandvik, Ulrika
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurosurgery.
    Koskinen, Lars-Owe
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurosurgery.
    Lundquist, Anders
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Blomstedt, Patric
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurosurgery.
    Thalamic and subthalamic DBS for essential tremor: where is the optimal target?2012In: Neurosurgery, ISSN 0148-396X, E-ISSN 1524-4040, Vol. 70, no 4, p. 840-846Article in journal (Refereed)
    Abstract [en]

    Background: The ventrolateral thalamus (Vim, ventral intermediate nucleus) is the traditional target for neurosurgical treatment of essential tremor (ET). The target has, however, varied substantially among different neurosurgeons.

    Objective: To evaluate the effect of deep brain stimulation (DBS) in the thalamus and posterior subthalamic area (PSA) in relation to electrode location.

    Methods: 36 (17Vim / 19 PSA) patients, with 44 DBS electrodes, were included in this retrospective study. The effect of stimulation was evaluated with standardized settings for each contact using items from the essential tremor rating scale (ETRS).

    Results: When each contact was evaluated regarding the treated hand with standardized stimulation, the electrode contact providing the best effect in the individual patient was in 54% located in the zona incerta (Zi) or radiation prelemniscalis (raprl) and in 12 % the Vim. 40 contacts provided a tremor reduction of >90%. Of these, 43% were located in the PSA and 18% in the Vim according to the Schaltenbrandt atlas. 37 of these 40 contacts were found in the PSA group.

    Conclusion: More contacts yielding an optimal effect were found in the PSA group than in the Vim. Many patients operated upon in the Vim got the best effect in a contact located in the PSA. This might suggest that the PSA is a more efficient target than the Vim.

  • 233.
    Segerstedt, Bo
    Umeå University, Faculty of Social Sciences, Statistics.
    On Conditioning and Ridge Estimation in Generalized Linear Models1991Licentiate thesis, monograph (Other academic)
  • 234.
    Segerstedt, Bo
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    On ordinary ridge regression in generalized linear models1992In: Communications in Statistics - Theory and Methods, ISSN 0361-0926, E-ISSN 1532-415X, ISSN 0361-0926, Vol. 21, no 8, p. 2227-2246Article in journal (Refereed)
    Abstract [en]

    In this paper it is shown that an ill-conditioned data matrix has similar effects on the parameter estimator when estimating generalized linear models as when estimating linear regression models. Asymptotically, the average length of the maximum likelihood estimator of a parameter vector increases as the conditioning of the covariance matrix deteriorates. A generalization of the ridge regression is suggested for maximum likelihood estimation in generalized linear models. In particular the existence of a ridge coefficient, k, such that the asymptotic mean square error of the generalized linear model ridge estimator is smaller than the asymptotic variance of the maximum likelihood estimator is shown. A numerical example illustrates the theoretical results

  • 235.
    Segerstedt, Bo
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Nyquist, Hans
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    On the conditioning problem in generalized linear models1992In: Journal of Applied Statistics, ISSN 0266-4763, E-ISSN 1360-0532, Vol. 19, no 4, p. 513-526Article in journal (Refereed)
    Abstract [en]

    When weights are assigned to a data matrix, as in the iterative least squares estimator of a generalized linear model, the condition of the data matrix is changed. In this paper a geometrical approach to studying the mechanisms which determine the changed condition is introduced. Specifically, it is found that in some cases strong multicollinearities can be weakened or eliminated by the weights while in other cases the weights can induce an ill-conditioning.

  • 236. Sellstrom, Eva
    et al.
    Arnoldsson, Goran
    Umeå University, Faculty of Social Sciences, Statistics.
    Bremberg, Sven
    Hjern, Anders
    Are there differences in mean birth weight between neighbourhoods in a Nordic welfare state: a 10 year cohort study.2007In: BMC Public Health, ISSN 1471-2458, Vol. 7, no 1, p. 267-Article in journal (Refereed)
  • 237. Sellstrom, J
    et al.
    Guldbrandsson, E
    Bremberg, K
    Hjern, S
    Arnoldsson, Göran
    Umeå University, Faculty of Social Sciences, Statistics.
    Association between childhood community safety interventions and hospital injury records: A multilevel study2003In: Journal of Epidemiology and Community Health, Vol. 57, p. 724-729Article in journal (Refereed)
  • 238.
    Sellström, E.
    et al.
    Department of Health Sciences, Mid Sweden University, Östersund, Sweden.
    O’Campo, P.
    Centre for Research on Inner City Health,The Li Ka Shing Knowledge Institute of St.Michael’s Hospital, Toronto, Canada.
    Muntaner, C.
    Faculty of Nursing, Department of Psychiatry and Public Health Sciences, University of Toronto,Toronto,Canada.
    Arnoldsson, Göran
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Hjern, A.
    Department of Women’s and Children’s Health, Uppsala university, Uppsala, Sweden .
    Hospital admissions of young persons for illicit drug use or abuse: does neighborhood of residence matter?2011In: Health and Place, ISSN 1353-8292, E-ISSN 1873-2054, Vol. 17, no 2, p. 551-557Article in journal (Refereed)
    Abstract [en]

    Adolescence constitutes a period of risk for drug use and drug use disorders. Previous research, largely focused on individual risk factors, has failed to include neighborhood structure in the study of determinants of youth drug use or abuse. A cohort of 76,693 adolescents ages 13–15 from 586 urban neighborhoods in Sweden were followed up for 12 years, from age 16 to age 28. Multilevel modeling was used to analyze neighborhood variations in hospital admissions due to illicit drug use or abuse. We found a variation of 8% by neighborhood economic status and the risk of being admitted to hospital increased 73% in low-compared to high-income neighborhoods. Our results suggest that neighborhood of residence in adolescence plays a significant role in predicting future health-related behaviors and that the need for drug abuse interventions at a neighborhood level is compelling.

  • 239.
    Sellström, Eva
    et al.
    Department of Health Sciences, MidSweden University, Östersund, Sweden.
    Arnoldsson, Göran
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Alricsson, Marie
    The Vårdal Institute, The Swedish Institute for Health Sciences, Lund University, Lund, Sweden.
    Hjern, Anders
    Centre for Epidemiology, Swedish National Board on Health and Welfare, Stockholm, Sweden.
    Obesity prevalence in a cohort of women in early pregnancy from a neighbourhood perspective2009In: BMC Pregnancy and Childbirth, ISSN 1471-2393, E-ISSN 1471-2393, Vol. 9, p. 37-Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The evidence of an association between neighbourhood deprivation and overweight is established for different populations. However no previous studies on neighbourhood variations in obesity in pregnant women were found. In this study we aimed to determine whether obesity during early pregnancy varied by neighbourhood economic status. METHODS: A register based study on 94,323 primiparous pregnant women in 586 Swedish neighbourhoods during the years 1992-2001. Multilevel technique was used to regress obesity prevalence on socioeconomic individual-level variables and the neighbourhood economic status. Five hundred and eighty-six neighbourhoods in the three major cities of Sweden, Stockholm, Göteborg and Malmö, during 1992-2001, were included. The majority of neighbourhoods had a population of 4 00010 000 inhabitants. RESULTS: Seven per cent of the variation in obesity prevalence was at the neighbourhood level and the odds of being obese were almost doubled in poor areas. CONCLUSION: Our findings supports a community approach in the prevention of obesity in general and thus also in pregnant women.

  • 240.
    Shafie, Termeh
    Umeå University, Faculty of Social Sciences, Statistics.
    On-site Sampling in Economic Valuation Studies2007Licentiate thesis, monograph (Other academic)
  • 241. Sjögren, H.
    et al.
    Eriksson, A.
    Broström, Göran
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Alm, K.
    Quantification of alcohol-related mortality in Sweden2001In: Alcohol and Alcoholism, ISSN 0735-0414, E-ISSN 1464-3502, p. 601-611Article in journal (Refereed)
  • 242.
    Stenberg, Anders
    et al.
    University of Stockholm.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Westerlund, Olle
    Umeå University, Faculty of Social Sciences, Department of Economics.
    Can adult education delay retirement from the Labour Market?2012In: Journal of Population Economics, ISSN 0933-1433, E-ISSN 1432-1475, ISSN 0933-1433, Vol. 25, no 2, p. 677-696Article in journal (Refereed)
    Abstract [en]

    We examine whether adult education delays retirement to potentially increase labour force participation among the elderly, a mechanism suggested in the OECD strategy for “active ageing” and the “Lisbon strategy” of the EU. Using register data from Sweden, we analyse transcripts from adult education for the period 1979–2004 and annual earnings 1982–2004. We match samples of treated individuals, in adult education 1986–1989, and untreated on the propensity score. The timing of exit from the workforce is assessed by non-parametric estimation of survival rates in the labour force. The results indicate no effects of adult education on the timing of retirement.

  • 243.
    Stenberg, Anders
    et al.
    University of Stockholm.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics. Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics. IFAU, Uppsala, Sweden.
    Westerlund, Olle
    Umeå University, Faculty of Social Sciences, Department of Economics. Jyväskylä University School of Business and Economics, Jyväskylä, Finland.
    Does formal education for older workers increase earnings?: evidence based on rich data and long-term follow up2014In: Labour, ISSN 1121-7081, E-ISSN 1467-9914, Vol. 28, no 2, p. 163-189Article in journal (Refereed)
    Abstract [en]

    Governments in Europe, Canada and the US have expressed an ambition to stimulate education of older. In this paper, we analyze if there are effects on annual earnings of formal education for participants aged 42-55 at the time of enrolment in 1994-1995. The analysis explores longitudinal population register data stretching from 1982 to 2007. The method used is difference-in-differences propensity score matching based on a rich set of covariates, including indicators of health and labor market marginalization. Our findings underline the importance of long follow up periods and imply positive effects for females, especially so for women with children, and no significant average earnings effects for males. These results differ from earlier studies but are stable to several alternative assumptions regarding unobservable characteristics. Data further indicate that the gender gap in our estimates may stem from differences in underlying reasons for enrolment.

  • 244.
    Stenberg, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Lundberg, Lina E.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Johansson, Anna-Mia
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Rydén, Patrik
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Umeå University, Faculty of Social Sciences, Department of Statistics.
    Svensson, Malin J.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Larsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Buffering of segmental and chromosomal aneuploidies in Drosophila melanogaster2009In: PLoS Genetics, ISSN 1553-7390, E-ISSN 1553-7404, Vol. 5, no 5Article in journal (Refereed)
    Abstract [en]

    Chromosomal instability, which involves the deletion and duplication of chromosomes or chromosome parts, is a common feature of cancers, and deficiency screens are commonly used to detect genes involved in various biological pathways. However, despite their importance, the effects of deficiencies, duplications, and chromosome losses on the regulation of whole chromosomes and large chromosome domains are largely unknown. Therefore, to explore these effects, we examined expression patterns of genes in several Drosophila deficiency hemizygotes and a duplication hemizygote using microarrays. The results indicate that genes expressed in deficiency hemizygotes are significantly buffered, and that the buffering effect is general rather than being mainly mediated by feedback regulation of individual genes. In addition, differentially expressed genes in haploid condition appear to be generally more strongly buffered than ubiquitously expressed genes in haploid condition, but, among genes present in triploid condition, ubiquitously expressed genes are generally more strongly buffered than differentially expressed genes. Furthermore, we show that the 4th chromosome is compensated in response to dose differences. Our results suggest general mechanisms have evolved that stimulate or repress gene expression of aneuploid regions as appropriate, and on the 4th chromosome of Drosophila this compensation is mediated by Painting of Fourth (POF).

  • 245.
    Stenlund, Hans
    et al.
    Umeå University, Faculty of Social Sciences, Statistics.
    Westlund, Anders
    Umeå University, Faculty of Social Sciences, Statistics.
    A Monte-Carlo Study of Some Sampling Designs1974Licentiate thesis, monograph (Other academic)
  • 246.
    Sundström, Anna
    et al.
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    Henriksson, Widar
    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.
    Alger, Susanne
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    "Ett givet inslag i förarutbildningen": Umeå universitet försvarar självvärderingen2008In: Mitt i trafiken, no 1, p. 33-33Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Sammanfattningsvis framstår det som en självklarhet att självvärdering ska vara ett inslag i såväl förarutbildning som förar­prov eftersom det utgör en väsentlig del i den nya kursplanen. Det står också klart att många vinster, både för lärandet och tra­fiksäkerheten, kan göras genom att införa självvärdering i utbildningen. Nästa steg är att diskutera hur detta ska genomföras i praktiken genom att finna sätt för hur självvärdering ska användas både i utbild­ning och i förarprov.

  • 247.
    Sundström, Anna
    et al.
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    Wiberg, Marie
    Umeå University, Faculty of Social Sciences, Department of Statistics. Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    Den svenska förarprövningens resultat: sambandet mellan kunskapsprovet och körprovet för underkända och godkända provtagare2005Report (Other academic)
    Abstract [sv]

    The Swedish driving-license test consists of a theory test and a practical test. The purpose of these tests is to investigate if the learner driver has the knowledge and abilities stated in the curriculum. The purpose of this study was threefold. Firstly, the purpose was to examine the relationship between the theory test and the practical test in a sample where testtakers that both passed and failed the theory test is included. Secondly, the purpose was to study the structure of the test score and the performance of the test-takers with regard to age, gender and driver education. Thirdly, the purpose was to investigate the relationship between self-assessed performance and test performance.

    The results on the theory test were similar compared to previous studies which indicated that the sample used was representative for the population of test-takers. However, many test-takers repeat the test several times and the percentage of test-takers taking the test for the first time has decreased. The results on the practical test in this study showed that pass rates have decreased compared to previous studies. One possible explanation for this is that the pass-rates are affected by the fact that test-takers who failed the theory test are included in the sample, and thus the test-takers limited theoretical knowledge is reflected in the decrease in pass-rates. When the relationship between the tests was examined the results indicated that the correlation was stronger than in previous studies. Moreover, the results showed that students from traffic school performed better on the theory test compared to private learners. The results on the practical test showed that students from traffic school, and those who combined professional education with private driver training, performed better than private learners. With regard to self-assessed performance, results indicated a relationship between performance on the theory test and self-evaluation. Testtakers performing high on the test rated their performance high and vice versa.

    The main conclusions of the study was that there is a relationship between theory and practice, in that sense that those performing well on the theory test perform better on the practical test compared to those performing less well on the theory test. Moreover, students from traffic school perform better on both the theory test and the practical test compared to private learners.

  • 248.
    Svensson, Ingrid
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Sjöstedt-de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Asymptotic properties of a stochastic EM algorithm for mixtures with censored data2010In: Journal of Statistical Planning and Inference, ISSN 0378-3758, E-ISSN 1873-1171, Vol. 140, no 1, p. 111-127Article in journal (Refereed)
    Abstract [en]

    Weak consistency and asymptotic normality is shown for a stochastic EM algorithm for censored data from a mixture of distributions under lognormal assumptions. The asymptotic properties hold for all parameters of the distributions, including the mixing parameter. In order to make parameter estimation meaningful it is necessary to know that the censored mixture distribution is identifiable. General conditions under which this is the case are given. The stochastic EM algorithm addressed in this paper is used for estimation of wood fibre length distributions based on optically measured data from cylindric wood samples (increment cores).

  • 249.
    Svensson, Maria
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Sundkvist, Göran
    Arnqvist, Hans J
    Björk, Elisabeth
    Blohmé, Göran
    Bolinder, Jan
    Henricsson, Marianne
    Nyström, Lennarth
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Public Health Sciences.
    Torffvit, Ole
    Waernbaum, Ingeborg
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Östman, Jan
    Eriksson, Jan W
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Signs of nephropathy may occur early in young adults with diabetes despite modern diabetes management: Results from the nationwide population-based Diabetes Incidence Study in Sweden (DISS)2003In: Diabetes Care, Vol. 26, p. 2903-2909Article in journal (Refereed)
  • 250. Svensson, Patrick
    et al.
    Broström, Göran
    Umeå University, Faculty of Social Sciences, Statistics.
    Oris, Michel
    Early-life conditions and social mobility in nineteenth century Belgium and Sweden2004Conference paper (Other (popular science, discussion, etc.))
234567 201 - 250 of 303
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