Confidence Intervals (easy question)

Goalie_Ca

Easy question but i'm being stupid somewhere. quite frustrating... enough to post it :surprise:

Basically the question is

Semiconductor wafer testing:
365 dies, 201 passed probing.
Assuming stable process calculate a 95% confidence interval for the proportion of all dies that pass the probe.

So x_bar = 201/365
std_dev = p*(1-p) = .228
n=356.

the answer in the book is .513,.615 and i'm not getting that. same for the next question and the one after lol.

HallsofIvy

The answer you say is in the book can't be right because it is not centered on the sample average: 201/365= 0.551 ((.513+ .615)/2= .564). Also your formula for standard deviation is wrong: you need a squareroot. Although I suspect it is a typo, is n 356 or 365?