Question 1: What is the research question? [3 marks] Question 2: Describe the study population. How were participants recruited? Are there any potential sources of bias related to the sample? If so, how would this have impacted on the observed results? [8 marks] Question 3: a) What is the exposure and how is it measured? [3 marks] b) What is the outcome and how is it measured? [3 marks] c) Discuss the potential for (differential and non-differential) measurement bias in this study, related to both the exposure and outcome variables. Did the authors address these potential sources of error? Describe the likely practical consequences on the results. [8 marks] Question 4: What are the main findings of the study? In your answer, include an explanation of the odds ratio (OR), incidence rate, incidence rate ratio (IRR) and 95% confidence interval, as appropriate. Are the results likely to be affected by chance variation? Why or why not?What variables did the authors consider as potential confounders? Explain the term "confounding" using one of these confounders to illustrate your answer. How do the authors deal with confounding in this study? Are there any other potential confounders not taken into account? Are the results likely to be affected by confounding? If so, describe how.external validity. Consider whether the findings can be applied to the actual population from which the study population was derived, and the target population; and whether the results can be applied to other relevant populations. [6 marks] Question 7: Comment on the overall contribution of your chosen paper to the current state of evidence on that issue. Discuss the extent to which the observed association between the exposure and the outcome can be attributed to causal and non-causal explanations. Consider the Bradford-Hill Criteria for Causality in your response. Explain how answers to previous questions support or detract from claims for causality and validity, and present any other issues you think are important.