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

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A doctor wants to estimate the mean HDL cholesterol of all​ 20-to​ 29-year-old females. How many subjects are needed to estimatethe mean HDL cholesterol within 3 points with 99% confidenceassuming s=12.5 based on earlier​ studies? Suppose the doctor wouldbe content with 90% confidence. How does the decrease in confidenceaffect the sample size​ required?

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4.4 Ratings (577 Votes)

for 99% confidence interval:

for 99 % CI value of z= 2.576
standard deviation σ= 12.50
margin of error E = 3
required sample size n=(zσ/E)2                                         = 116.0

for 90% confidence interval:

for 90 % CI value of z= 1.645
standard deviation σ= 12.50
margin of error E = 3
required sample size n=(zσ/E)2                                         = 47.0

hence decreasing  confidence interval to 90% will decrease the requirement of sample size.


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