Cameron is including only parents with an undergraduate degree in his study. What method of control is he using?

The method of control Cameron is using by including only parents with an undergraduate degree in his study is known as holding constant. This approach involves keeping certain variables consistent across the study participants to isolate the effect of the independent variable on the dependent variable. By restricting the sample to parents with similar educational backgrounds, Cameron eliminates the variability that might arise from differences in education levels. This helps to ensure that any observed effects are more likely attributed to the independent variable rather than confounding influences related to education.

Other methods like randomization would involve randomly assigning participants to different conditions, matching would pair participants based on specific characteristics, and statistical adjustment would apply statistical techniques to account for the influence of certain variables. However, holding constant directly involves selecting specific criteria for inclusion in the study, which is what Cameron is doing with the educational level of the parents.