random numbers, random number generation,

'4 A simulation study to determine appropriate linking methods for adaptive testing items was designed. Responses of examinees of three group sizes for four test lengths were simulated. Three basic data sets were created: (a) randomly sampled data set, (b systematically sampled data set, and (c) selected data set. Three categories of evaluative criteria were used: fidelity of parameter estimation, asymptotic ability estimates. root-mea n-square error of estimates, and the correlation between true and estimated ability. Test length appeared to be relatively more important to calibrition effectiveness than was sample size. efficiency analyses suggested that increases in test length were at least three to four times as effective in improving calibrafion efficiency as proportionate increases in calibration sample sizes. ability estimation (an equivalent-groups procedure) were somewhat more effective than the others and that the equivalent-tests method was typically no better than not linking at all. Analyses using the relative efficiency criteria suggested that the equivalent-groups procedures were superior to the equivalent-tests procedures and that those using Bayesian scoring prucedires were slightly superior to the others tested. Efficiency loss due to linking error was always less than that due to item calibration error and although test length and sample size had a definite effect on calibration efficiency. no strong effects appear with respect to linking efficiency. For the systematically sampled data set. the anchor-test and anchor-group methods were considered along with the equivalence methods. In terms of linking efficiency, the anchor-test method produced the most efficient item pools. The anchor-grou 4 method resulted in efficiencies equivalent to those of the anchor-test procedure if large groups were used. but with smaller groups the efficiencies dropped somewhat. The equivalence methods were somewhat less efficient than either of the anchor methods. Bayesian scoring was preferred over the maximum-likelihood scoring procedure. An application of the .1, results of this research to a practical linking problem was described with equivalent-groups linking. An anchor-test linking method was suggested for adding items at later times. I

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