Student Solutions Manual for Devore's Probability and Statistics for Engineering and the Sciences, 9th
9th Edition
ISBN: 9798214004020
Author: Jay L. Devore
Publisher: Cengage Learning US
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Textbook Question
Chapter 8.2, Problem 20E
Lightbulbs of a certain type are advertised as having an average lifetime of 750 hours. The price of these bulbs is very favorable, so a potential customer has decided to go ahead with a purchase arrangement unless it can be conclusively demonstrated that the true average lifetime is smaller than what is advertised A random sample of 50 bulbs was selected, the lifetime of each bulb determined, and the appropriate hypotheses were tested using Minilab, resulting in the accompanying output.
| Variable | N | Mean | StDev | SE Mean | Z | p-value |
| lifetime | 50 | 738.44 | 38.20 | 5.40 | −2.14 | 0.016 |
What conclusion would be appropriate for a significance level of .05? A significance level of .01? What significance level and conclusion would you recommend?
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Because of high production-changeover time and costs, a director of manufacturing must convince management that a proposed manufacturing method reduces costs before the new method can be implemented.
The current production method operates with a mean cost of $260 per hour. A research study will measure the cost of the new method over a sample production period.
(a) Develop the null and alternative hypotheses most appropriate for this study.
Ho: H 260
Hai us 260
Ho: Hs 260
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H: u < 260
Ho: H = 260
H: µ # 260
(b) Comment on the conclusion when H, cannot be rejected.
There is not enough evi
to conclude that the new method reduces costs. Management should consider implementing the new
O There is not enough evidence to conclude that the new method reduces costs. Management should not consider implementing the new method.
O There is enough evidence to conclude that the new method reduces costs. Management should not consider implementing the new method.
There is enough…
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Chapter 8 Solutions
Student Solutions Manual for Devore's Probability and Statistics for Engineering and the Sciences, 9th
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