SOLUTION: A plant manager at a local factory makes widgets, and he wants to propose a more efficient manufacturing process. He would like you to find the estimate time it takes to make the

Question 210180: A plant manager at a local factory makes widgets, and he wants to propose a more efficient manufacturing process. He would like you to find the estimate time it takes to make the widget under the new proposal. So far, he has some data that says the fastest widget production time is 500 seconds, and the slowest is 560 seconds. He would like to estimate the mean assembly time to within 4 seconds with a 95% confidence interval but questions what sample size he'll need to have. Assume that the widget assembly times are normally distributed. Can you recommend a sample size for him?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A plant manager at a local factory makes widgets, and he wants to propose a more efficient manufacturing process. He would like you to find the estimate time it takes to make the widget under the new proposal. So far, he has some data that says the fastest widget production time is 500 seconds, and the slowest is 560 seconds. He would like to estimate the mean assembly time to within 4 seconds with a 95% confidence interval but questions what sample size he'll need to have. Assume that the widget assembly times are normally distributed. Can you recommend a sample size for him?
-------------------------
You need to know the standard deviation and are only given a
range to work with.
---
6*sigma = 560-500
sigma = 10
--------------------
E = z*sigma/sqrt(n)
---
So sqrt(n) = z*sigma/E
n = [z*sigma/E]^2
----
n = [1.96*10/4]^2
---
n = 24
=========================
Cheers,
Stan H.
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