Examination for Professional Practice of Psychology (EPPP) Practice Test

To estimate a predictor's criterion-related validity coefficient with a reliability coefficient of 1.0, which formula would you use?

1. Spearman-Brown prophecy formula

2. Correction for attenuation formula

3. Coefficient of concordance

4. Kuder-Richardson Formula 20

The correct answer is: Correction for attenuation formula

The correct approach to estimating a predictor's criterion-related validity coefficient when the reliability coefficient is 1.0 involves using the correction for attenuation formula. The rationale behind this is that the correction for attenuation formula is specifically designed to adjust the correlation between a predictor and an outcome, accounting for the reliability of both measures involved. When the reliability coefficient is 1.0, it indicates perfect reliability, meaning the measure does not have any measurement error affecting the results. Consequently, applying the correction for attenuation effectively allows you to ascertain the true validity of the predictor without the influence of any measurement error. The other options listed serve different purposes or are applicable in other contexts. The Spearman-Brown prophecy formula is used for estimating the reliability of a test when splitting it into two halves, not for correcting validity coefficients. The coefficient of concordance is concerned with ranking data and assessing agreement among raters, while the Kuder-Richardson Formula 20 is focused on estimating the reliability of dichotomous (yes/no) items. These formulas do not directly address the relationship between a predictor's validity and its reliability as the correction for attenuation does.