A doctor wants to estimate mean HDL cholesterol of all 20 to 29 year old females
ID: 3158022 • Letter: A
Question
A doctor wants to estimate mean HDL cholesterol of all 20 to 29 year old females. How many subjects are needed to estimate the mean HDL cholesterol within 4 points with 99% confidence assuming s = 12.8 based on earlies 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 squarebox subjects.(Round upto nearest subject) A 90% confidence level requires squarebox subjects.(Round upto nearest subject) How does the decrease in confidence affect the sample size required? The sample size is the same for all levels of confidence. Decreasing the confidence level decreases the sample size needed. Decreasing the confidence level increases the sample size needed.Explanation / Answer
a)
Note that
n = z(alpha/2)^2 s^2 / E^2
where
alpha/2 = (1 - confidence level)/2 = 0.005
Using a table/technology,
z(alpha/2) = 2.575829304
Also,
s = sample standard deviation = 12.8
E = margin of error = 4
Thus,
n = 67.94134119
Rounding up,
n = 68 [ANSWER]
******************************************
b)
Note that
n = z(alpha/2)^2 s^2 / E^2
where
alpha/2 = (1 - confidence level)/2 = 0.05
Using a table/technology,
z(alpha/2) = 1.644853627
Also,
s = sample standard deviation = 12.8
E = margin of error = 4
Thus,
n = 27.70476497
Rounding up,
n = 28 [ANSWER]
********************************
c)
Hence,
OPTION B. Decreasing the confidence level decreases the sample size needed. [ANSWER]
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.