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 o. (a) Assuming this to be the case, if a sample of 81 modified bars resulted in a sample average yield point of 8417 Ib, compute a 90% CI for the true average yield point of the modified bar. (Round your answers to one decimal place.) (b) How would you modify the interval in part (a) to obtain a confidence level of 92%? (Round your answer to two decimal places.) -Select-- v should be changed to
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 o. (a) Assuming this to be the case, if a sample of 81 modified bars resulted in a sample average yield point of 8417 Ib, compute a 90% CI for the true average yield point of the modified bar. (Round your answers to one decimal place.) (b) How would you modify the interval in part (a) to obtain a confidence level of 92%? (Round your answer to two decimal places.) -Select-- v should be changed to
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
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Transcribed Image Text: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 o.
(a) Assuming this to be the case, if a sample of 81 modified bars resulted in a sample average yield point of 8417 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 92%? (Round your answer to two decimal places.)
|---Select--
v should be changed to
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