The Effect of Class Size on Reliability Estimates of College-Students Course Grades

This study aimed at investigating the effect of class size on reliability estimates of college-students course grades. Course grades were considered as composite scores with congeneric parts: first exam score, second exam score, final exam score, and attendance score. The reliability of these scores was estimated using Raju formula with three or more known lengths. To conduct this study, 63 classes were sampled from among all classes at Jadara University in Jordan in the second semester 20011/2012. These classes represented small, medium and big sizes with equal number of classes for each size. The results of this study showed that, in general, reliability estimates for all classes were low. The mean reliability estimate for all classes was 0.55 with 25% of classes being classified as having low reliability, and 65% of classes as having unacceptable reliability. The mean reliability estimate for small classes was 0.68, whereas it decreased to 0.41 for big classes. Finally, the relationship between class size and reliability estimates was shown to be significant, with small classes having higher estimates of reliability.