Question 824539
A production line is designed on the assumption that the difference between mean assembly times for two operations is five minutes. Independent tests for the two assembly operations yielded the following results. 
Operation A: n1 = 25, xbar1 = 19.2, s1 = .73. 
Operation B: n2 = 25, xbar2 = 13.68, s2 = .53. 
At the 2% significant level, test the hypothesis that the difference between the mean assembly times is u1 - u2 = 5 minutes.
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Ho: u1-u2 = 5
Ha: u1-u2 # 5
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Sample stat:: xbar1-xbar2 = 19.2-13.68 = 5.52
test statistic:: z(5.52) = (5.52-5)/sqrt[0.73^2/25 + 0.53^2/25] = 2.8821
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p-value = 2*P(z > 2.8821) = 2*normalcdf(2.8821,100) = 0.0039
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Conclusion: Since the p-value is less than 2%, reject Ho.
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Cheers,
Stan H.
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