A Forensic Psychologist Is Attempting to Assess the Validity of a New

Essay

A forensic psychologist is attempting to assess the validity of a new test of police aptitude. The test is given to a random sample of first-day trainees during their orientation session at the police academy. At the end of the 2 month training program each subject is evaluated by the academy's director and rank-ordered on the basis of overall proficiency. The data follow. $$\begin{array} { c l c } \text { Subj\# } & \text { Test Score } & \text { Ranking } \\1 & 55 & 8 \\2 & 60 & 3 \\3 & 45 & 6 \\4 & 75 & 2 \\5 & 43 & 5 \\6 & 34 & 10 \\7 & 48 & 7 \\8 & 62 & 1 \\9 & 50 & 4 \\10 & 46 & 9\end{array}$$
-Is this a valid test? . Point out to your students that this is actually a positive correlation as far as the validity is concerned. The only reason the negative sign appears is because in the ranking process, the highest score gets a 1 (a metrically low number) and the lowest score gets a 10 (a metrically higher number). Ask your students to rank order the test scores, and then again compute the Spearman, using only the two sets of ranks. At that point, that correlation of -.733 now has a positive sign.