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 withi

Question

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 4 points with 99 % confidence assuming s equals 19.4 based on earlier studies? Suppose the doctor would be content with 90 % confidence. How does the decrease in confidence affect the sample size required?
LOADING... Click the icon to view a partial table of critical values. ( 0.05 1.645)
A 99% confidence level requires how many subjects?

Answer 1

confidence coefficient for 99% is 2.58

 

 2.58 * 19.4/sqrt(n) = 0.04

 

2.598*19.4/0.04 = sqrt(n)

 

 ( 2.598*19.4/0.04)^2  = n

 

1587676

 

 

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confidence coefficient for 90% is 1.64

 

(1.64*19.4/0.04)^2 = 632661.16