An observational study compares injuries (e.g. frequency and severity assessed using a questionnaire that yields a numeric score) between students using High Intensity Interval Training (HIIT) and students following a traditional strength training regimen for one year. The research team wants to assess if the association between injuries during the study period and regimen (HIIT vs. traditional) is consistent between students with extensiveprior injury history and those with less extensive prior injury history. What can you as the statistician do to assess if difference in mean injury scores during the study period between the two groups is homogeneous across the range of prior injury history?

a.

Include the student's prior injury history score in a multiple linear regression withregimen (HIIT vs. traditional) to control for effect modification

b.

Include the student's prior injury history score in a multiple linear regression withregimen (HIIT vs. traditional) to control for confounding

c.

Include an interaction term for student's prior injury history score by regimen (HIIT vs. traditional) in a multiple linear regression to assess effect modification

d.

Exclude student's with prior injury history from the analysis