Shulman Steel Corporation makes bearings that are supplied to other companies. One of the machines makes bearings that are supposed to have a diameter of 4 inches. The bearings that have a diameter of either more or less than 4 inches are considered defective and are discarded. When working properly, the machine does not produce more than 7% of bearings that are defective. The quality control inspector selects a sample of 200 bearings each week and inspects them for the size of their diameters. Using the sample proportion, the quality control inspector tests the null hypothesis p < .07 against the alternative hypothesis p > .07, where p is the proportion of bearings that are defective. He always uses a 2% significance level. If the null hypothesis is rejected, the machine is stopped to make any necessary adjustments. One sample of 200 bearings taken recently contained 22 defective bearings.
a. Using a 2% significance level, will you conclude that the machine should be stopped to make necessary adjustments?
b. Perform the test of part a using a 1% significance level. Is your decision different from the one in part a?
Comment on the results of parts a and b.

  • CreatedAugust 25, 2015
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