chapter 1

Chapter 13: Nonlinear and Multiple Regression69.a. Based on a scatter plot (below), a simple linear regression model would not beappropriate. Because of the slight, but obvious curvature, a quadratic model wouldprobably be more appropriate.350Temperat250150500 100 200 300 400Pressureb. Using a quadratic model, a Minitab generated regression equation is2yˆ= 35.423 + 1.7191x− .0024753x, and a point estimate of temperature whenpressure is 200 is y ˆ = 280. 23 . Minitab will also generate a 95% prediction interval of(256.25, 304.22). That is, we are confident that when pressure is 200 psi, a single valueof temperature will be between 256.25 and 304.22 ο F .70.5.182a. For the model excluding the interaction term, R = 1−= . 394 , or 39.4% of the8.55observed variation in lift/drag ratio can be explained by the model without the interactionaccounted for. However, including the interaction term increases the amount of variation3.072in lift/drag ratio that can be explained by the model to R = 1 − = . 641, or64.1%.8.55432