Refer to the Journal of Engineering for Gas Turbines and Power (Jan. 2005) study of gas turbines augmented with high-pressure inlet fogging, Exercise 8.29. The data on engine heat rate (kilojoules per kilowatt per hour) is saved in the GASTURBINE file. Recall that the researchers classified gas turbines into three categories: traditional, advanced, and aero derivative. Suppose you want to compare the heat rate distributions for traditional and aero derivative turbine engines.

a. Demonstrate that the assumptions required to compare the mean heat rates using a t test are likely to be violated.

b. A MINITAB printout of the nonparametric test to compare the two heat rate distributions is shown above. Interpret the p-value of the test shown at the bottom of the printout.

Data from Exercise 8.29

During periods of high electricity demand, especially during the hot summer months, the power output from a gas turbine engine can drop dramatically. One way to counter this drop in power is by cooling the inlet air to the gas turbine. An increasingly popular cooling method uses high-pressure inlet fogging. The performance of a sample of 67 gas turbines augmented with high-pressure inlet fogging was investigated in the Journal of Engineering for Gas Turbines and Power (Jan. 2005). One measure of performance is heat rate (kilojoules per kilowatt per hour). Heat rates for the 67 gas turbines are listed in the table on the bottom of page. Suppose that a standard gas turbine has, on average, a heat rate of 10,000 kJ/kWh. Conduct a test to determine if the mean heat rate of gas turbines augmented with high-pressure inlet fogging exceeds 10,000 kJ/kWh. Use α = .05.

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Mann-Whitney Test and Cl: TRAD-HR, AERO-HR N Median TRAD-HR 39 11183 AERO-HR 7 12414 Point estimate for ETA1-ETA2 is -1125 95.3 Percent CI for ETA1-ETA2 is (-2358, 1448) W = 885.0 Test of ETA1 = ETA2 vs ETA1 not = ETA2 is significant at 0.3431 The test is significant at 0.3431 (adjusted for ties)