Graziano & Raulin
Research Methods (9th edition)
Correlation and Regression
This screen shows the data structure for computing a test-retest reliability coefficient. In this case, we have two scores on the same measure from each of 12 participants. The scores were taken two weeks apart. The product-moment correlation between these variables is the index of test-retest reliability.
Note that if we had two raters, we would structure the data in the same way and compute the same product-moment correlation to get interrater reliability.
