Question: AMCO Drilling Equipment Inc. is a Texas-based company that makes drilling equipment for the oil and gas industry. One item that the company makes is a coupling for use on natural gas drills. AMCO has 2 machines that make these couplings, which we will call machine 1 and machine 2. Quality Control at AMCO claims that machine 2 provides couplings with higher average diameters. If the test determines that machine 2 has an average diameter larger than machine 1, the managers will have maintenance attempt to adjust the diameters downward or they will replace the machine. To test this claim, AMCO obtained a random sample of 100 couplings from machine 1 and 100 couplings from machine 2. The data was analyzed in a statistical package and the output is below.

a. Formulate the null and alternative hypotheses. Label the claim.

b. Test the claim at the 5% level of significance. Use either the p-value method or rejection regions. List the numbers you calculated. State the decision rule.

c. State a conclusion about the claim in terms of the “real-world” significance of the problem. Will machine 2 have to be adjusted or replaced?