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:

x 72 78 80 86 88 92 y 4.8 7.2 9.5 14.5 15.7 17.9 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 828F, the true average number of hours of chiller operation is less than 12. The appropriate hypotheses are then H0: a 1 b(82) 5 12 versus Ha: a 1 b(82) , 12 Use the statistic t 5 a 1 b1822 2 12 sa1b1822 which has a t distribution based on (n 2 2) df when H0 is true, to test the hypotheses at significance level .01.