The article “Performance Test Conducted for a Gas Air-Conditioning System” (American Soc...

The article “Performance Test Conducted for a Gas Air-Conditioning System” (American Society of Heating, Refrigerating, and Air Conditioning Engineering [1969]: 54) reported the following data on maximum outdoor temperature (x) and hours of chiller operation per day ( y) for a 3-ton residential gas air-conditioning system:

Suppose that the system is actually a prototype model, and the manufacturer does not wish to produce this model unless the data strongly indicate that when maximum outdoor temperature is 82°F, the true average number of hours of chiller operation is less than 12. The appropriate hypotheses are then

which has a t distribution based on (n - 2) df when H₀ is true, to test the hypotheses at significance level .01.