A prospective cohort study with a duration of 10 years found a vitamin supplement reduced the risk of cardiovascular disease. However, subsequent studies, including high-quality randomised controlled trials, have found the vitamin supplement has no effect on the risk of cardiovascular disease. Please provide potential explanations as to why the results from the initial cohort study are inconsistent with later findings by referring to 1. random sampling error; 2. selection bias; 3. measurement error; and 4. confounding. You are provided with marks for explaining what the issue is and for explaining how the issue could be relevant in explaining the results. (3 marks for each issue for a total of 12 marks). Please set your answers out under each of the four headings.