Alfred Kinsey and his colleagues interviewed thousands of individuals regarding their sexual behavior and attitudes. Which data collection method did they utilize?

The answer is: in-depth interviews.

Explanation:

Although Kinsey and his colleagues collected data from thousands of men and women, they didn't use surveys as a data collection method. Instead they used in-depth, face-to-face interviews with each one of the research subjects, in order to gather qualitative data. His data collection method has been considered flawed or biased because he used a sample of convenience, which means his strategy for selecting subjects was opportunistic and the sample can't be considered representative. However, whether the sample is considered representative or not, the amount of data he and his team gathered from the thousands of interviews makes the study a landmark of research on human sexuality.