Browsing by Author "Wingersky, Marilyn S."

Now showing 1 - 3 of 3
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    Comparison of IRT true-score and equipercentile observed-score "equatings"
    (1984) Lord, Frederic M.; Wingersky, Marilyn S.
    Two methods of ’equating’ tests are compared, one using true scores, the other using equipercentile equating of observed scores. The theory of equating is discussed. For the data studied, the two methods yield almost indistinguishable results.
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    An investigation of methods for reducing sampling error in certain IRT procedures
    (1984) Wingersky, Marilyn S.; Lord, Frederic M.
    The sampling errors of maximum likelihood estimates of item response theory parameters are studied in the case when both people and item parameters are estimated simultaneously. A check on the validity of the standard error formulas is carried out. The effect of varying sample size, test length, and the shape of the ability distribution is investigated. Finally, the effect of anchor-test length on the standard error of item parameters is studied numerically for the situation, common in equating studies, when two groups of examinees each take a different test form together with the same anchor test. The results encourage the use of rectangular or bimodal ability distributions, and also the use of very short anchor tests.
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    A study of pre-equating based on item response theory
    (1982) Bejar, Isaac I.; Wingersky, Marilyn S.
    The study reports a feasibility study using item response theory (IRT) as a means of equating the Test of Standard Written English (TSWE). The study focused on the possibility of pre-equating, that is, deriving the equating transformation prior to the final administration of the test. The three-parameter logistic model was postulated as the response model and its fit was assessed at the item, subscore, and total score level. Minor problems were found at each of these levels; but, on the whole, the three-parameter model was found to portray the data well. The adequacy of the equating provided by IRT procedures was investigated in two TSWE forms. It was concluded that pre-equating does not appear to present problems beyond those inherent to IRT-equating.