Alzheimer's disease is a progressive disease of the brain. The journal eCAM (Nov. 2006) published an article that critiqued the quality of the methodology used in studies on Alzheimer's treatment. For each in a sample of 13 studies, the quality of the methodology was measured on the Wong scale, with scores ranging from 9 (low quality) to 27 (high quality). The data are shown in the table below.

a. Estimate, with a 99% confidence interval, the mean quality ( of all studies on the treatment of Alzheimer's disease. Interpret the result.

b. According to the researchers, a study with a Wong score below 18 used a methodology that "fails to support the author's conclusions" about the treatment of Alzheimer's. Use Wilson's adjustment to estimate the proportion of all studies on the treatment of Alzheimer's disease with a Wong score below 18. Construct a 99% confidence interval around the estimate and interpret the result.

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22 21 18 15 19 20 15 20 17 20 21 19 20