subject: Studies at the University of Wisconsin [print this page] Studies at the University of Wisconsin Studies at the University of Wisconsin
Stephen Elliott, professor at the University of Wisconsin, summarized findings from research he and his colleagues have conducted on the effects of accommodations on test performance. All four studies compared performance of students with disabilities and students without disabilities. A key characteristic of the studies was that they relied on a design in which each student took the test under both accommodated and nonaccommodated conditions, thus serving as his or her own "control." To facilitate this aspect of the research design, multiple equivalent test forms were used, and each subject took two forms of the test-one form under accommodated conditions and one under nonaccommodated conditions.
The researchers used counterbalanced designs; in their investigations, randomizing the order of the accommodated versus nonaccommodated conditions as well as the form that was used under the two conditions. The researchers used "effect sizes" to summarize their findings. An effect size is a ratio in which the numerator is the difference between two means (e.g., the difference between the mean for students without disabilities and the mean for students with disabilities on a given test; or the difference between the means when students take the test with accommodations and without accommodations). The denominator of the ratio is a standard deviation, typically that of the overall population or of the "majority" or comparison group. The researchers used a commonly accepted scheme to categorize effect sizes into large (> .80), medium (.40 to .80), small (< .40), zero, and negative effects (Cohen and Cohen, 1983). A common framework for interpreting the validity of accommodations is based on discussions by Phillips (1994) and Shepard, Taylor, and Betebenner (1998) of ways to evaluate whether scores obtained with and without accommodations have comparable meanings.
As described by Shepard et al., if accommodations are working as intended, an interaction should be present between educational status (e.g., students with disabilities and students without disabilities) and accommodation conditions (e.g., accommodated and not accommodated). For this part, learning a foreign language needs a leaning tools, many students choose Rosetta Stone German and Rosetta Stone Hebrew to learn German and Hebrew. The accommodation should improve the average score for a group of students with disabilities, but should have little or no effect on the average score of a group of non-disabled students. If an accommodation improves the performance of both groups, providing it only to certain students (those with a specific disability) is considered to be unfair. Figure 6-1 portrays a visual depiction of the 2 x 2 experimental design used to test for this interaction effect. An interaction effect would be said to exist if the mean score for examinees in group C were higher than the mean score for group A, and the mean scores for groups B and D were similar. The interaction effect was used in Elliott's studies (and others in this chapter) as the criterion for judging the validity of scores from acommodated administration.
