In answering the following question, you may find it helpful to draw on the facts in Grandjean et al. (1998) or Myers et al. (2003). Answer with a specific example, rather than attempting to provide a perfectly general explanation.

1a. Explain how randomization helps avoid confounding. (one paragraph answer)

1b. Explain the key distinction between an experiment and an observation. Explain the benefits and drawbacks of each. (one paragraph answer)

1c. Is is possible for an observational study to be randomized in a useful way? An experimental study? (one paragraph answer)