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Confidence Intervals (easy question) 
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#1
Jul2404, 08:48 PM

P: 105

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*(1p) = .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. 


#2
Jul2604, 07:47 AM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 39,495

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?



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