Stainless steels can be susceptible to stress corrosion cracking under certain conditions. A materials engineer is interested in determining the proportion of steel alloy failures that are due to stress corrosion cracking. a) In the absence of preliminary data, how large a sample must be taken so as to be sure that a 98% confidence interval will specify the proportion to within ±0.05? b) In a sample of 200 failures, 30 of them were caused by stress corrosion cracking. Find a 98% confidence interval for the proportion of failures caused by stress corrosion cracking. c) Based on the data in part (b), estimate the sample size needed so that the 98% confidence interval will specify the proportion to within ±0.05.
Stainless steels can be susceptible to stress corrosion cracking under certain conditions. A
materials engineer is interested in determining the proportion of steel alloy failures that are
due to stress corrosion cracking.
a) In the absence of preliminary data, how large a sample must be taken so as to be sure
that a 98% confidence interval will specify the proportion to within ±0.05?
b) In a sample of 200 failures, 30 of them were caused by stress corrosion cracking. Find
a 98% confidence interval for the proportion of failures caused by stress corrosion
cracking.
c) Based on the data in part (b), estimate the
confidence interval will specify the proportion to within ±0.05.
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