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?
a. 0.40
b. 0.50
c.0.80
d. 0.90
Reliability = True variance/Observed variance
Therefore:
R = 40/50 = .8
0.40
R=0.8
To estimate the reliability of a test using classical test theory, we can use the formula:
Reliability = (True Variance) / (True Variance + Error Variance)
Given that the observed variance is 50 and the true variance is 40, we can calculate the error variance by subtracting the true variance from the observed variance:
Error Variance = Observed Variance - True Variance
= 50 - 40
= 10
Now, we can substitute the values into the formula:
Reliability = 40 / (40 + 10)
= 40 / 50
= 0.80
Therefore, the estimated reliability of the test is 0.80, which corresponds to option c.