Tuesday, July 28, 2015

Say you want to get a confidence interval for the difference of two proportions.

To get p^ you take x/n, so the first two are quite simple
p1^ = 25.176 = .142
 p2^ = 32/143 = .224


 for 90% CI you use 1.645 for zcritical
formula is p1^ - p2^ +/- 1.645(sqrt(p1^q1^/n1 + p2^q2^/n2))
if you do this correctly for the data we have you get
-.082 +/- .071850965
(-.154, -.010)

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