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.

:yuck: :yuck:

[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?