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Suppose you are interested to determine the effect of social media usage on body mass index among Ulw students. Explain how you would conduct each of the following kinds of studies. Be concise but do not omit any essential details in the design of your study. a) Randomized controlled trial b) Case control study c) Cohort study d) Cross sectional study e) Explain why you might be concerned, in your observational studies, about reverse causation. What about confounding variables or third factor causation? Explain why these might also be valid concerns