Register January 2016 No. 721
Chapter PI 11
Regression Formula for Calculating Significant Discrepancy Scores
Information needed for Calculation:
IQ/Ability Score   =       SD of IQ/Cognitive Test =     (SDi)
Achievement Score   =       SD of Achievement Test =     (SDa)
            Correlation between tests =   0.   (r)*
- See PDF for diagram PDFExpected Achievement = (SDa/SDi)r(IQ-100)+100 = ______
Discrepancy = Expected Achievement - Obtained Achievement Score       =
- See PDF for diagram PDF - See PDF for diagram PDFSD Discrepancy = SDa 1-r2                 =
- See PDF for diagram PDFCut-off:
Discrepancy / SD Discrepancy =
If number is greater than 1.75, there is a significant discrepancy between achievement and ability scores
* If correlation between tests is unknown, use .62
When the test publisher provides tables for significant differences between ability and achievement scores (such as with the Weschler Intelligence Scale for Children- 3 and the Weschler Individual Achievement Test), these tables may be used in lieu of this formula. Cut-offs should be derived using a 1.75 Standard Error of Estimate (SEe) criterion so that the difference between expected and obtained scores in the bottom 4% of the distribution meet the standard for a significant discrepancy (i.e. 1.75 SEe units below the expected score).
Published under s. 35.93, Stats. Updated on the first day of each month. Entire code is always current. The Register date on each page is the date the chapter was last published.