=+Once the simple linear regression model has been judged useful by the model utility test discussed in Section 11.2, the estimated model can be used as the basis for further inferences. Let x denote a particular value of the independent or predictor variable x.

In this section, we show how to obtain a confidence interval for the mean y value when x: 25.5 31.5 37.5 43.5 49.5 55.5 yfw: 25.7 43.2 55.3 62.9 68.6 73.2 ysw: 26.4 40.1 50.2 57.4 62.7 67.3 x: 61.5 67.5 73.5 79.5 85.5 91.5 yfw: 76.7 79.4 81.8 83.7 85.1 86.5 ysw: 71.4 74.7 77.8 80.3 82.3 84.1 x: 97.5 103.5 109.5 115.5 121.5 127.5 yfw: 87.7 88.6 89.6 90.5 90.7 91.2 ysw: 85.5 86.6 87.9 89.0 89.9 90.6 x: 133.5 139.5 145.5 151.5 157.5 yfw: 91.9 92.5 93.1 93.9 94.7 ysw: 91.2 91.8 92.3 92.8 93.3