Practice problems…
Percentages, # correct/ total # of items
Z-scores, (observed score – mean)/ standard deviation
T-scores, (Z*10) + 50
Percentile, [cf + .5 (f i)]/N
Dr. Day’s class (N = 40) just took a History & Systems exam with 50 items. The mean score was 35 and the SD was 5.
Calculate percentage scores, Z-scores, T-scores, and Percentiles for the following students.
Raw Score # of persons with the same score # of persons scoring below their score
Darius 25 1 2
Kay 35 4 16
Scroll down for the answers…
Percentage Z T Percentile
Darius 50 -2 30 .08 (7.50%)
Kay 70 0 50 .46 (46.25%)