Astudy 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:
a. the placebo effect. b. a stratified analysis. c. a double-blind observational study. d. a matched pairs experiment.

D. a matched pairs experiment.

Step-by-step explanation:

A matched pairs experiment can be designed when there are only two possible treatment conditions (Screen A and Screen B) within an experiment and the subjects can be accordingly grouped into pairs (Both sides of the body of a same person, since both sides present the same skin complexion). Within each pair (both sides of the subject's body), subjects are randomly assigned (coin toss) to different treatments.

Therefore, this experiment is an example of a matched pairs experiment.

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i'm 75% sure the answer is 1,1 to both lines.

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step-by-step explanation: