A study attempts to compare two sunscreens Each of 50 subjec

A study attempts to compare two sunscreens. Each of 50 subjects with varying skin complexions will use both sunscreens—Screen A on one side of his or her body and Screen B on the other side. For each subject, a coin is tossed in order to determine which side receives Screen A and which receives Screen B. Researchers measure the amount of ultraviolet light exposure over both treated areas for each subject. This is an example of:

the placebo effect. a stratified analysis. a double-blind observational study. a matched pairs experiment.

A study attempts to compare two sunscreens. Each of 50 subjects with varying skin complexions will use both sunscreens—Screen A on one side of his or her body and Screen B on the other side. For each subject, a coin is tossed in order to determine which side receives Screen A and which receives Screen B. Researchers measure the amount of ultraviolet light exposure over both treated areas for each subject. This is an example of:

the placebo effect. a stratified analysis. a double-blind observational study. a matched pairs experiment.

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