Ralph has just taken two achievement tests.He scored at the 90th percentile on the Ohio Reading Test ORT).He scored at the 50th percentile on the California Mathematics Inventory CMI).Can we conclude that Ralph has higher achievement in reading than in mathematics?
A)Yes, because a percentile rank of 90 is well above average, whereas a percentile rank of 50 is only average.
B)Yes, provided that both tests have been shown to have content validity for the curriculum at Ralph's school.
C)No, because the two percentile ranks are both essentially "average" scores.
D)No, because the norm groups for the two tests are probably different.

Question

Quizplus · Accepted Answer

The norm groups for the two tests likely differ, meaning Ralph's performance is compared to different sets of peers for each test, making direct comparison of percentile ranks across subjects unreliable.

Ralph Has Just Taken Two Achievement Tests