Question 1043988: 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 2 points with 99% confidence assuming σ=13.3? 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 how many subjects? (Round up to the nearest whole number as needed.)
A 95% confidence level requires how many subjects? (Round up to the nearest whole number as needed.)
How does the decrease in confidence affect the sample size required?
A.The lower the confidence level the smaller the sample size.
B.The lower the confidence level the larger the sample size.
C.The sample size is the same for all levels of confidence.
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! The lower the confidence the smaller the sample size needed, A.
the standard error is z*s/sqrt(n), and we want that to equal 2
z*s/sqrt(n)=2; z^2*s^2=4*n, by squaring everything and multiplying both sides by n.
n=z^2*s^2/4
z(.995)=2.576
sigma=13.3
n=293.45 or 294
---------------------
Everything is the same for 95% confidence except the z value is 1.96
3.8416*(13.3)^2/4=169.88 or 170, rounding to the higher number.
|
|
|
