Which method is NOT a means of controlling extraneous variables?

The option that is not a means of controlling extraneous variables is conducting interviews with participants. This method does not directly influence the study's variables or their relationships, and therefore, it does not serve to control for extraneous factors that could affect the outcomes of the research. Interviews are typically used for gathering qualitative data or insights into participants' experiences, rather than controlling variables within an experimental design.

In contrast, randomly selecting subjects helps to distribute extraneous variables evenly across all groups, minimizing their potential impact on the results. Using a homogeneous sample restricts the diversity of subjects to those with similar characteristics, thereby reducing variability that could confound the results. Manipulating the independent variable is fundamental in experimental research, as it seeks to establish causality between the independent and dependent variables while controlling for external influences. Each of these methods directly addresses the management of variables within the study, unlike conducting interviews, which focuses on data collection rather than variable control.