An Intelligence Test Was Given To A Combined Group Of 4 Th 5 Th And 6 Th Grade C

An intelligence test was given to a combined group of 4th, 5th, and 6th grade children. The average was 65 and the SD was 3. Based on the combined results, the reliability of the test was found to be 0.70, (for grades combined). Later, the test was given to another 5th grade in the same community. What should the reliability coefficient be for this 5th grade sample alone?

A. Above 0.70 due to cross validation

B. Below 0.70 due to pooling of error

C. Around 0.67 due to SD error

D. It depends on the validity of the test

Please help, and let me know how you came to your answer. Thank you!