Question

A doctor wants to estimate the mean HDL cholesterol of all​ 20- to​ 29-year-old females. How many subjects are needed to estimate the mean HDL cholesterol within 2 points with 99 % confidence assuming s equals 13.4 based on earlier​ studies? 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. ​(Round up to the nearest​ subject.)

A 90% confidence level requires __ subjects. ​(Round up to the nearest​ subject.)

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

A. Decreasing the confidence level increases the sample size needed.

B. The sample size is the same for all levels of confidence.

C. Decreasing the confidence level decreases the sample size needed.

Answer 1

given data are:-

margin or error (E) = 2

a).z critical value for 99% confidence level, both tailed test be:-

number of subjects required by a 99% confidence level is :-

b).z critical value for 90% confidence level, both tailed test be:-

number of subjects required by a 90% confidence level is :-

c).Decreasing the confidence level decreases the sample size needed.

[ as we know that as confidence interval increase, in order to be more confident we need to take a relatively large sample ]

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