0.25/1 points | Previous Answers DevoreStat9 7.E.006 My Notes Ask Your Teacher O

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0.25/1 points | Previous Answers DevoreStat9 7.E.006 My Notes Ask Your Teacher 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 = 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) Assuming this to be the case, if a sample of 36 modified bars resulted in a sample average yield point of 8435 lb, compute a 90% CI for the true average yield point of the modified bar. (Round your answers to one decimal place.) lb (b) How would you modify the interval in part (a) to obtain a confidence level of 94%? (Round your answer to two decimal places.) The value of z should be changed to You may need to use the appropriate table in the Appendix of Tables to answer this question. Need Help?Read It Talk to a Tutor Submit Answer Save Progress Practice Another Version

Explanation / Answer

The statistical software output for this problem is:

One sample Z summary confidence interval:
: Mean of population
Standard deviation = 100

90% confidence interval results:

Hence,

90% confidence interval will be:

(8407.6, 8462.4) lb

Mean n Sample Mean Std. Err. L. Limit U. Limit 36 8435 16.666667 8407.5858 8462.4142

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