ISE 225 Engineering Statistics I
Homework #3
Fall Semester 2010
Due: Wednesday, September 15
1.
Complete the following exercises from Hines, Montgomery, Goldsman, and Borror:
1040
The life in hours of a 75W light bulb is known to be approximately normally
distributed, with a standard deviation of
σ
= 25 hours.
A random sample of 20 bulbs
has a mean life of
1014
x
=
hours.
a)
Construct a 95% twosided confidence interval on the mean life.
b)
Construct a 95% lowerconfidence interval on the mean life.
1042
Suppose that in Exercise 1040 we wanted to be 95% confident that the error in
estimating the mean life is less than 5 hours.
What sample size should be used?
112
part a) only, evaluate the test by using a critical point
The yield of a chemical process is being studied.
The variance of the yield is known
from previous experience with this process to be 5 (units of
σ
2
= percentage
2
).
The past
five days of plant operation have resulted in yields (in percentages): 91.6, 88.75, 90.8,
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This note was uploaded on 01/04/2011 for the course ISE 31602D taught by Professor Kurtpalmer during the Fall '10 term at USC.
 Fall '10
 KurtPalmer

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