Five data collectors were assigned to measure the weights and heights of 30 sixth graders. On the day of data collection, the height and weight measurements were conducted twice on the same child, but taken by a different data collector each time The lead investigator wanted to examine if there were differences in the height and weight measurements collected between data collectors. The investigator was examining the:


a internal consistency

b. test-retest reliability

c. inter-rater reliability

d. intra-rater reliability