434 Chapter 9: Regression
(c) Determine an interval that, with 95 percent confidence, will contain the
response when the inputs arex 1 =10. 2 andx 2 =17.52.The cost of producing power per kilowatt hour is a function of the load factor
and the cost of coal in cents per million Btu. The following data were obtained
from 12 mills.Load Factor Cost of Power
(in percent) Coal Cost
84 14 4.1
81 16 4.4
73 22 5.6
74 24 5.1
67 20 5.0
87 29 5.3
77 26 5.4
76 15 4.8
69 29 6.1
82 24 5.5
90 25 4.7
88 13 3.9(a) Estimate the relationship.
(b) Test the hypothesis that the coefficient of the load factor is equal to 0.
(c) Determine a 95 percent prediction interval for the power cost when the load
factor is 85 and the coal cost is 20.53.The following data relate the systolic blood pressure to the age (x 1 ) and weight
(x 2 ) of a set of individuals of similar body type and lifestyle.Age Weight Blood Pressure
25 162 112
25 184 144
42 166 138
55 150 145
30 192 152
40 155 110
66 184 118
60 202 160
38 174 108(a) Test the hypothesis that, when an individual’s weight is known, age gives
no additional information in predicting blood pressure.