An epidemiologist wishes to estimate the association between residential proximity to green spaces (the existence of parks, playgrounds, grass elds, woodlands, etc. near one's place of residence) and the incidence rate of major depressive episodes among a cohort of 10-year-old US. children followed for 5 years. Sixty percent of the cohort members were female, and 40% of the cohort members were male. Females and males were equally likely to live near green spaces. The exposed group is green space = yes. The unexposed group is green space = no. The incidence rate of major depressive episodes among children who lived near green spaces was 70 per 1,000 person*years. The incidence rate of major depressive episodes among children who did not live near green spaces was 85 per 1,000 person *years. The incidence rate of major depressive episodes among females was 90 per 1,000 person*years. The incidence rate of major depressive episodes among males was 65 per 1,000 person*years. 2a. Calculate the crude (unadjusted) rate ratio for the association between residential proximity to green spaces and the incidence rate of major depressive episodes. 2b. Is the crude rate ratio that you calculated in 2a biased due to confounding by sex? Explain your reasoning. [HINT: I have not provided you with the data to calculate an adjusted rate ratio to answer this question you need to read the bullets and evaluate whether the criteria for confounding have been satised]