- #1
Poke
Homework Statement
Each day a quality engineer selects a random sample of 60 power supplies from the day's production, measures their output voltages, and computes a 90% confidence interval for the mean output voltage of all the power supplies manufactured that day. What is the probability that more than 15 of the confidence intervals constructured in the next 210 days will fail to cover the true mean? Hint: Use the normal approximation.
Homework Equations
z=\Frac{x-\miu}{\sigma}
The Attempt at a Solution
First, X~Bin(n,p), as np >10, it follows Normal distribution, X~N(np, np(1-p))
np is \miu,
\sqrt{np(1-p)} is \signma
then Z = \frac{x-\miu}{\sigma}, it is the area of left tail