1. Two variables in a study are said to be confounded if

2. In an experiment, an observed difference between groups that is to large to be due to chance alone is called

3. The essential difference between an experiment and an observational study is that.

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punithg05Lv10

18 Jun 2023

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Observational studies have suggested that vitamin E reduces the risk of heart disease. Careful experiments, however, showed that vitamin E has no effect. According to a commentary in the Journal of the American Medical Association: Vitamin E enters the category of therapies that were promising in epidemiologic and observational studies, but failed to deliver in adequately powered randomized controlled trials. As in other studies, the “healthy user’’ bias must be considered; i.e., the healthy lifestyle behaviors that characterize individuals who care enough about their health to take various supplements are actually responsible for the better health, but this is minimized with the rigorous trial design.

Explain, by describing lurking variables, why observational studies suggest that Vitamin E therapy reduces the risk of heart disease. Note that a randomized controlled trial is a type of experiment.

carminejellyfish837

For his Statistics class experiment, researcher J. Gilbert decided to study how parents’ income affects children’s performance on standardized tests like the SAT. He proposed to collect information from a random sample of test takers and examine the relationship between parental income and SAT score.

a) Is this an experiment? If not, what kind of study is it?

b) If there is relationship between parental income and SAT score, why can’t we conclude that differences in score are caused by differences in parental income?