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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