Borg-Warner manufactures hydroelectric miniturbines that generate low-cost, clean electric power from the energy in small rivers and streams. One of the models was known to produce an average of 25.2 kilowatts of electricity.
Recently the model's design was improved, and the company wanted to test whether the model's average electric output had changed. The company had no reason to suspect, a priori, a change in either direction. A random sample of 115 trial runs produced an average of 26.1 kilowatts and a standard deviation of 3.2 kilowatts.
Carry out a statistical hypothesis test, give the p-value, and state your conclusion. Do you believe that the improved model has a different average output?