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 22 points with 99% confidence assuming σ=11.1? 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.

Answer 1

The concept is based on calculation of Z score

for 99% confidence level

= 22 points
STD DEV() = 11.1
Z VALUE = 2.5758 for 99%
SO, n = [ z* /]^2 = (2.5758 * 11.1/22)^2 = 1.6889 = 2 subjects

for 90% confidence level

Z VALUE = 1.64 for 90%

SO, n = [ z* /]^2 = (1.64 * 11.1/22)^2 =0.6846 = 1 subject

Difference in subject = 2-1 = 1 subject.

Note: kindly check the value of point in question , 22 point , seems in correct., The solved answer is true with given data.