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#1
07-15-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,867 Threads: 149 Thanked 2,107 Times in 1,049 Posts Reputation: 2127
Sample Size and Standard Deviation

Cholesterol levels are measured on a random sample of 1,000 persons, and the sample standard deviation is calculated. A second survey were repeated in the same population, but the sample size tripled to 3,000.

Which of the following is true?

a. The new sample standard deviation would tend to be smaller than the first and approximately about one-third the size.
b. The new sample standard deviation would tend to be larger than the first and approximately about three times the size.
c. The new sample standard deviation would tend to be larger than the first, but we cannot approximate by how much.
d. None of the above is true because there is no reason to believe one standard deviation would tend to be larger than the other.

#2
07-15-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 646 Threads: 52 Thanked 762 Times in 256 Posts Reputation: 773

standard deviation is inversely related to the number of people in the group.

so id go with
. The new sample standard deviation would tend to be smaller than the first and approximately about one-third the size.

 Tags Biostatistics-Epidemiology, Step-2-Questions

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