1.A physical therapist wants to determine the difference in the proportion of men and women who participate in regular sustained physical activity. What sample size should be obtained if she wishes the estimate to be within two percentage points with 95?% ?confidence, assuming that

?(a) she uses the estimates of 22.7?% male and 18.4?% female from a previous?year?

?(b) she does not use any prior?estimates?

?(a) n=

?(Round up to the nearest whole?number.)

?(b) n=

?(Round up to the nearest whole?number.)

2.A doctor wants to estimate the mean HDL cholesterol of all?20- to?29-year-old females. How many subjects are needed to estimate the mean HDL cholesterol within 2 points with 99% confidence assuming s=14.5 based on earlier?studies? Suppose the doctor would be content with 90% confidence. How does the decrease in confidence affect the sample size?required?

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ded. Partial Critical Value Table X eded Level of Confidence, Critical Value, Za /2 (1 -() . 100% Area in Each Tail, 2 90% 0.05 1.645 95% 0.025 1.96 99% 0.005 2.575 Print Done