A teacher split a 50-item test into odd and even items, scored each half, and then correlated odd scores with even scores.The correlation coefficient was .55.What is the estimated reliability for the full 50-item test?
A) .80
B) .71
C) .69
D) .65
E) .60

Question

Quizplus · Accepted Answer

The estimated reliability for the full 50-item test can be calculated by doubling the correlation coefficient between the two halves (even and odd items) and subtracting the result from 1. This is known as Spearman-Brown formula.

So, 2(.55) - 1 = .1.1. This suggests that the full 50-item test has an estimated reliability of .71 (or 71%). Therefore, the best choice is B.

A Teacher Split a 50-Item Test into Odd and Even