Statistics
posted by John .
A random sample of 250 men yielded 175 who said they'd ridden a motorcycle at some time in their lives, while a similar sample of 215 women yielded only 43 that had done so. Find a 99% confidence interval for the difference between the proportions of men and women who have ridden motorcycles.
.4688 ± .085
.5 ± .112
.5 ± .103
.5 ± .085
.5 ± .078

Let's look at your data:
n1 = 250
n2 = 215
p1 = 175/250
p2 = 43/215
Formula:
CI99 = (p1  p2) ± 2.58 √(p1(1p1)/n1 + p2(1p2)/n2)
Substitute the values into the formula and calculate. (Convert all fractions to decimals.)
You should be able to select your answer once you have determined the interval. 
.5 ± .103

.5 } .103, because, as the math guru said the formula is (p1  p2) } 2.58 ã(p1(1p1)/n1 + p2(1p2)/n2), the 2.58 comes from the zscore table. The question doesn't want you to solve the whole formula, just the first and last.. (175/250)(43/215)=.5 and the ã(p1(1p1)/n1 + p2(1p2)/n2=.1026887336
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