On the basis of extensive tests, the yield point of a particular type of mild steel-reinforcing bar is known to be normally distributed with o = 100. The composition of the bar has been slightly modified, but the modification is not believed to have affected either the normality or the value of a. (a) Assuming this to be the case, if a sample of 64 modified bars resulted in a sample average yield point of 8461 lb, compute a 90% CI for the true average yield point of the modified bar. (Round your answers to one decimal place.) | Ib (b) How would you modify the interval in part (a) to obtain a confidence level of 96%? (Round your answer to two decimal places.) The value of z vv should be changed to

Glencoe Algebra 1, Student Edition, 9780079039897, 0079039898, 2018
18th Edition
ISBN:9780079039897
Author:Carter
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Chapter10: Statistics
Section: Chapter Questions
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**Statistical Analysis of Yield Points in Steel-Reinforcing Bars**

**Background Information:**
Extensive testing has shown that the yield point of a specific type of mild steel-reinforcing bar follows a normal distribution with a standard deviation (\(\sigma\)) of 100. The composition of the bar underwent slight modifications; however, these changes are not believed to affect the normality or standard deviation.

**Statistical Tasks:**

**(a)** If a sample of 64 modified bars results in an average yield point of 8461 pounds (lb), compute a 90% confidence interval (CI) for the true average yield point of the modified bar. Round your answers to one decimal place.

- Confidence Interval: ( _____ , _____ ) lb

**(b)** To alter the interval in part (a) for a 96% confidence level, determine the new value of \(z\). Round your answer to two decimal places.

- The value of \(z\): The value of \(z\) should be changed to _____.

**Notes:**
- A graph or diagram is not included with the text. The exercise requires computation using statistical methods pertinent to confidence intervals for means in a normally distributed sample. 
- Ensure calculations consider sample size, standard deviation, and desired confidence levels for accuracy in the statistical analysis.
Transcribed Image Text:**Statistical Analysis of Yield Points in Steel-Reinforcing Bars** **Background Information:** Extensive testing has shown that the yield point of a specific type of mild steel-reinforcing bar follows a normal distribution with a standard deviation (\(\sigma\)) of 100. The composition of the bar underwent slight modifications; however, these changes are not believed to affect the normality or standard deviation. **Statistical Tasks:** **(a)** If a sample of 64 modified bars results in an average yield point of 8461 pounds (lb), compute a 90% confidence interval (CI) for the true average yield point of the modified bar. Round your answers to one decimal place. - Confidence Interval: ( _____ , _____ ) lb **(b)** To alter the interval in part (a) for a 96% confidence level, determine the new value of \(z\). Round your answer to two decimal places. - The value of \(z\): The value of \(z\) should be changed to _____. **Notes:** - A graph or diagram is not included with the text. The exercise requires computation using statistical methods pertinent to confidence intervals for means in a normally distributed sample. - Ensure calculations consider sample size, standard deviation, and desired confidence levels for accuracy in the statistical analysis.
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