According to classical test theory, if the observed variance of a test is 50 and the true variance is 40, what is the estimated reliability of the test?

Question

Quizplus · Accepted Answer

The formula for estimating reliability using classical test theory is:

reliability = (true score variance) / (true score variance + error variance)

Since we are given that the true variance is 40 and the observed variance is 50, the error variance is:

error variance = observed variance - true variance
error variance = 50 - 40
error variance = 10

Plugging these values into the reliability formula, we get:

reliability = 40 / (40 + 10)
reliability = 40 / 50
reliability = 0.8 or 80%

Therefore, the correct answer is C) 80.

According to Classical Test Theory, If the Observed Variance of a Test