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 sunjects are needed to estimate the HDL cholesterol within 3 point with 99% confidence assumming =10.1?

Suppose the doctor would be content with 95% confidence. How does thedecrease in confidence affect the sample size required?

A 99% confidences level level requires ___subjects.
(Round up to the nearest whole number as needed.)

A doctor wants to estimate the HDL cholesterol of all 20-to 29- year-old females. How many sunjects are needed to estimate the HDL cholesterol within 3 point with 99% confidence assumming =10.1?

Suppose the doctor would be content with 95% confidence. How does thedecrease in confidence affect the sample size required?

A 99% confidences level level requires ___subjects.
(Round up to the nearest whole number as needed.)

Explanation / Answer

standard deviation =10.1

let the required no of subjects be n

standard deviation of sample mean = /n = 10.1/n

margin of error for 99% confidence level is 2.575*(standard deviation of sample mean) i.e 2.575*(10.1/n)

so 2.575*(10.1/n) = 3

n = (2.575*10.1/3) =8.669

n = 75.15 i.e n=76

A 99% confidences level level requires 76 subjects.

margin of error for 95% confidence level is 1.96*(standard deviation of sample mean) i.e 1.96*(10.1/n)

so 1.96*(10.1/n) = 3

n = (1.96*10.1/3) =6.599

n =43.54 i.e n=44

A 95% confidences level level requires 44 subjects.

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