The quality-control supervisor at a wire company selects a sample to test the br
ID: 3224895 • Letter: T
Question
The quality-control supervisor at a wire company selects a sample to test the breaking strength of the wire. A random sample of 18 wires is collected. The sample mean is 5,300 pounds, and the sample standard deviation is 210 pounds. The breaking strengths of the wire have a normal distribution. Use a 95% confidence interval to estimate the population mean breaking strength of the wire produced by this company. Show your work.
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Identify: X = _____pounds s = _____ pounds n = _____
Identify the critical Z or t values for a 95% confidence interval. ____________________________
List the formula for a confidence interval to estimate the mean of the population.
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Use a 95% confidence interval to estimate the mean phone call length for the population of phone calls made by the customers.
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Explanation / Answer
X bar= 5300 s 210 n 18 z(A/2)= 1.959963985 CI = mean +- z(a/2)*(sd/sqrt(n)) lower =5300-1.96*(210/SQRT(18)) 5202.985 upper =5300+1.96*(210/SQRT(18)) 5397.015
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