<PRE><B>Question 208222</B>
The standard error of the mean for a characteristic of a sample of 100 identity theft victims is 30. In order to cut the standard error to 15, we would: 
a. Increase the sample size to 200
b. Increase the confidence interval 
c. Increase the sample size to 400
d. Decrease the sample size to 50
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SE = t*[s/sqrt(n)]
If SE = 30 and n = 100 you have
30 = t*[s/10]
ts = 300
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If you want SE to be 15
you need:
15 = ts/sqrt(n)
15 = 300/sqrt(n)
sqrt(n) = 20
n = 400
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Cheers,
Stan H.</PRE>