*Create a table that portrays the similarities and differences between a controlled experiment and a quasi-experiment.*Describe how you would conduct a nested case-control study of low socioeconomic status as a risk factor for teenage pregnancy.*Explain what is meant by the statement that cohort studies overcome the problem of temporality, which is not addressed by other types of observational study designs. You satisfy temporality of cause and effect, one of the causal criteria—not done in other observational studies.*What are some of the practical issues that influence the design of a cohort study?*Explain the purposes of blinding and randomization in clinical trials.*Describe the phases of a clinical trial to license a vaccine or new medicine.*What is meant by a crossover design? Distinguish between a planned and unplanned crossover.