The overall aim was to examine effects of differences in group ability and features of the anchor test formon equating bias and the standard error of equating (SEE) using both real and simulated data. Chainedkernel equating, Postratification kernel equating, and Circle-arc equating were studied. A collegeadmissions test with four different anchor test forms administered at three test administrations was used.The simulation study examined the differences in ability of the test groups, and differences in the anchortest form with respect to item difficulty and discrimination. In the empirical study, the equated valuesfrom the three methods only slightly differed. The simulation study indicated that an easier anchor testform and/or an easier regular test form, and anchor items with a wider spread in difficulty, negativelyaffected the SEE and bias. The ability level of groups was also important. Equating with only less or morecapable groups resulted in high SEEs at higher and lower test scores, respectively. The discussion includespractical recommendations to whom an anchor test should be given if there is a choice and how to selectan anchor test form which have equating as primary purpose.