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11. 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 the body and Screen B on the other side. For each subject, a coin is tossed 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 and compare. a. This study is a (2 pts) i. observational study ii. completely randomized experiment iii. block (not matched pairs) experiment iv. matched pairs experiment b. The response variable in this study is (2 pts) i. Sunscreen ii. Amount of ultraviolet light exposure ifi. The 50 subjects c. The explanatory variable in this study is (2 pts) i. Sunscreen ii. Amount of ultraviolet light exposure iii. The 50 subjects