Confidence Intervals (easy question)

by Goalie_Ca
Tags: confidence, intervals
Goalie_Ca is offline
Jul24-04, 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*(1-p) = .228

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

Phys.Org News Partner Science news on
Simplicity is key to co-operative robots
Chemical vapor deposition used to grow atomic layer materials on top of each other
Earliest ancestor of land herbivores discovered
HallsofIvy is offline
Jul26-04, 07:47 AM
Sci Advisor
PF Gold
P: 38,879
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?

Register to reply

Related Discussions
confidence to find? Introductory Physics Homework 4
Confidence Intervals Set Theory, Logic, Probability, Statistics 3
confidence intervals Set Theory, Logic, Probability, Statistics 1
Statistics: Confidence Intervals Calculus & Beyond Homework 1
Confidence Intervals Set Theory, Logic, Probability, Statistics 4