Question

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

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

33

points with

99 %

confidence assuming

sigma equals 10.8 question markσ=10.8?

Suppose the doctor would be content with

95 %

confidence. How does the decrease in confidence affect the sample size​ required?

A​ 99% confidence level requires

nothing

subjects.

​(Round up to the nearest whole number as​ needed.)

Solution :

Given that,

Population standard deviation = = 10.8

Margin of error = E = 0.33

1)

Z/2 = 2.576

sample size = n = [Z/2* / E] 2

n = [2.576 * 10.8 / 0.33]2

n = 7108

Sample size = n = 7108

2)

Z/2 = 1.96

sample size = n = [Z/2* / E] 2

n = [1.96 * 10.8 / 0.33]2

n = 4115

Sample size = n = 4115

the decrease in confidence level the sample size​ is decreased

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