Tests and Assessments: CAN DIFFERENT TESTS FOR ABILITY/ACHIEVEMENT BE COMPARED?

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Lacey:  When the school is trying to determine ability/achievement can they use to different tests? For example: Can they use the RIAS 2 to determine ability and then compare it to KTEA 3 for achievement? Or do they have to use the same test to determine “ability/achievement”? If two different tests are used…how do you know the two scores will be credible when compared to one another?

  1. Yes, you can use two “different” tests to document an ability/achievement discrepancy. Tests that are normed and developed together (such as the Woodcock-Johnson Cognitive and Achievement tests) usually have higher correlation/agreement than tests that aren’t developed together–but different tests can be used successfully as long as the correlation is taken into account. For example, the KTEA 3 manual provides correlation tables for the KABC-II and the DAS-II. Because it doesn’t report correlations with the RIAS-2 best practice would be to use the default correlation of .62 to compute ability/achievement discrepancy. The school psychologist should be able to provide you with all of this information for the chosen tests.

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