Statistics for Engineers and Scientists
4th Edition
ISBN: 9780073401331
Author: William Navidi Prof.
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 5, Problem 16SE
In a study of the lifetimes of electronic components, a random sample of 400 components are tested until they fail to
a. An approximate 95% confidence interval for the mean lifetime of this type of component is from 306.3 to 433.7 hours.
b. About 95% of the sample components had lifetimes between 306.3 and 433.7 hours.
c. If someone takes a random sample of 400 components, divides the sample standard deviation of their lifetimes by 20, and then adds and subtracts that quantity from the sample mean, there is about a 68% chance that the interval so constructed will cover the mean lifetime of this type of component.
d. The z table can’t be used to construct confidence intervals here, because the lifetimes of the components don’t follow the normal curve.
e. About 68% of the components had lifetimes in the interval 370 ± 650 hours.
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Chapter 5 Solutions
Statistics for Engineers and Scientists
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