A doctor wants to estimate the HDL cholesterol of all 20-to 29-year-old females.

Question

A doctor wants to estimate the HDL cholesterol of all 20-to 29-year-old females. How many subjects are needed to estimate the HDL cholesterol within 4 points with 9% confidence assuming 1657 Suppose the doctor would be content with 90% confidence. How does the decrease in confidence affect the sample size required? A 99% confidence level requires subjects. Round up to the nearest whole number as needed.) A 90% confidence level requires subjects. Round up to the nearest whole number as needed.) How does the decrease in confidence affect the sample size required? 0 A. The sample size is the same for all levels of confidence O B. The lower the confidence level the smaller the sample size. O C. The lower the confidence level the larger the sample size

Explanation / Answer

a)margin of error E =4

for 99% CI ; z=2.5758

therefore sample size n=(z*std deviation/E)2 =~115

b) for 90% CI ; z=1.6449

therefore sample size n=(z*std deviation/E)2 =~ 47

option B is correct; lower the confidence level the smaller the sample size

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