Question

standard 6: i can plan fair experiments, check if results really show cause and effect, and make sure the study is done ethically
does regularly taking aspirin help protect people against heart attacks? does regularly taking beta - carotene help prevent cancer? the physicians health study i was a medical experiment that helped answer these questions. the subjects in this experiment were 21,996 male physicians. each of the physicians was assigned to take an aspirin or an aspirin - like placebo. likewise, each of the physicians was assigned to take beta - carotene or a beta - carotene - like placebo. the physicians were followed for several years and researchers recorded if each of the physicians had a heart attack or developed cancer.

1. why was it necessary to perform an experiment rather than simply asking the doctors whether or not they take aspirin and beta - carotene regularly?
2. identify the four treatments in this experiment.
3. explain the purpose of the control group in this experiment.

Explanation:

1.

Asking doctors may have recall bias (they might misremember) and confounding variables (other lifestyle factors they don't mention). An experiment controls variables better.

The treatments are based on the two substances (aspirin and beta - carotene) and their placebos.

The control group (placebo groups) is used to compare against the treatment groups. It helps determine if the actual substances (aspirin or beta - carotene) have an effect.

Answer:

An experiment controls variables (like other health - related behaviors) better. Just asking doctors may have recall bias (they may not accurately remember their aspirin and beta - carotene use over time) and confounding variables (e.g., a doctor who takes aspirin regularly might also exercise more, which could affect heart attack risk).

2.