You are studying the effect of physical activity (exposure) on the risk of developing cardiovascular disease (CVD, outcome) and suspect that gender might modify this effect. You conduct a study and obtain the following results:

Among men:

	CVD cases	Total # of people under observation
Physically active	50	1000
Not physically active	120	800

Among women:

	CVD cases	Total # of people under observation
Physically active	30	1200
Not physically active	110	1000

- Calculate the risk (i.e. cumulative incidence) of CVD for active and inactive individuals in each gender group (you should have four estimates of cumulative incidence: one for active men, one for active women, one for inactive men and one for inactive women). Please show your calculations and units.

- Calculate the relative risk (RR) and absolute risk (AR) of cardiovascular disease for active compared to inactive individuals in each gender group, again showing your work (you should have two RRs and two ARs-- one of each for men and women).

- Is gender an effect measure modifier of the association between physical activity and cardiovascular disease? Why or why not? On what scale is it an effect measure modifier-- additive, multiplicative, or both?

- Using the three criteria for confounding discussed in Module 11, discuss if gender is also a confounder of the association between physical activity and cardiovascular disease. Remember that a variable can be a confounder, an effect measure modifier, both, or neither.

- Based on your answers to questions 3 and 4, what should you do about gender in your analysis? I.e. should you adjust for it? Which risk ratio should you report-- the overall one or the gender-specific one? Justify your chosen strategy.