Headability is the ability of a cylindrical piece of material to be shaped into the head of a bolt, screw, or other cold-formed part without cracking. The article “New Methods for Assessing Cold Heading Quality” ( Wire J. Intl ., Oct. 1996: 66–72) described the result of a head-ability impact test applied to 30 specimens of aluminum killed steel and 30 specimens of silicon killed steel. The sample mean headability rating number for the steel specimens was 6.43, and the sample mean for aluminum specimens was 7.09. Suppose that the sample standard deviations were 1.08 and 1.19, respectively. Do you agree with the article’s authors that the difference in headability ratings is significant at the 5% level (assuming that the two headability distributions are normal)?

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Probability and Statistics for Eng...

9th Edition
Jay L. Devore
Publisher: Cengage Learning
ISBN: 9781305251809
BuyFind

Probability and Statistics for Eng...

9th Edition
Jay L. Devore
Publisher: Cengage Learning
ISBN: 9781305251809

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Chapter
Section
Chapter 9, Problem 75SE
Textbook Problem

Headability is the ability of a cylindrical piece of material to be shaped into the head of a bolt, screw, or other cold-formed part without cracking. The article “New Methods for Assessing Cold Heading Quality” (Wire J. Intl., Oct. 1996: 66–72) described the result of a head-ability impact test applied to 30 specimens of aluminum killed steel and 30 specimens of silicon killed steel. The sample mean headability rating number for the steel specimens was 6.43, and the sample mean for aluminum specimens was 7.09. Suppose that the sample standard deviations were 1.08 and 1.19, respectively. Do you agree with the article’s authors that the difference in headability ratings is significant at the 5% level (assuming that the two headability distributions are normal)?

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Chapter 9 Solutions

Probability and Statistics for Engineering and the Sciences
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