(Solved): please explain 20 of 25 > Avobenzone is one of the active ingredients in several commercially availa ...

20 of 25 > Avobenzone is one of the active ingredients in several commercially available sunscreens. It can be absorbed into the bloodstream when sunscreen is applied to the skin. The Food and Drug Administration has expressed concern about the safety of absorbing too much avobenzone. Amounts less than or equal to 0.5 ng/mL. (nanograms absorbed per milliliter applied) are considered acceptable. Researchers recruited 12 healthy volunteers to investigate avobenzone absorption for two different commercially available sunscreens: a spray and a cream. Subjects were randomly assigned to one of the two sunscreens, with 6 subjects for each. Subjects had 2 milligrams of sunscreen per 1 cm² applied to 75% of their body surface area (area outside of normal swimwear). The amount of avobenzone absorbed into the bloodstream after 6 hours was then measured for each subject. Four of the six subjects receiving the spray had avobenzone levels exceeding 0.5 ng/mL, and one of the six subjects receiving the cream had levels exceeding 0.5 ng/mL. The z test for "no difference" in the two proportions exceeding 0.5 ng/mL against "the two proportions differ" has O= 1.84, P < 0.055. Oz=1.76, P < 0.05. z = 1.76, 0.05 < P <0.10.