A student received a score of 85 on a classroom test where the mean was 70 and the standard deviation was 10.The test was found to have a reliability coefficient of .64.Which of the following statements would correctly express the accuracy of the student's obtained score? There are
A) 50 chances out of 100 that the true score is included by the range of scores from 72 to 78.
B) 68 chances out of 100 that the true score is included by the range of scores from 75 to 95.
C) 68 chances out of 100 that the true score is included by the range of scores from 79 to 91.
D) 75 chances out of 100 that the true score is included by the range of scores from 79 to 91.
E) 95 chances out of 100 that the true score is included by the range of scores from 79 to 91.

Question

Quizplus · Accepted Answer

First, we need to calculate the standard error of measurement (SEM) using the formula SEM = SD * sqrt(1 - reliability). 
SEM = 10 * sqrt(1 - 0.64) = 6.0
Then, we need to calculate the confidence interval (CI) using the formula CI = score +/- (SEM * z-score). The z-score for a 68% CI is 1, so we can calculate the CI as follows:
CI = 85 +/- (6.0 * 1) = 79 to 91
Therefore, we can say that there is a 68% chance that the true score for the student is included within the range of scores from 79 to 91. Answer choice C correctly expresses the accuracy of the student's obtained score.

A Student Received a Score of 85 on a Classroom