Solved: The following data were collected during an

Chapter 12, Problem 12-74

(choose chapter or problem)

The following data were collected during an experiment to determine the change in thrust efficiency ( y, in percent) as the divergence angle of a rocket nozzle (x) changes:y 24.60 24.71 23.90 39.50 39.60 57.12 x 4.0 4.0 4.0 5.0 5.0 6.0 y 67.11 67.24 67.15 77.87 80.11 84.67 x 6.5 6.5 6.75 7.0 7.1 7.3 (a) Fit a second-order model to the data. (b) Test for significance of regression and lack of fit using 0.05. (c) Test the hypothesis that 11 0, using 0.05. (d) Plot the residuals and comment on model adequacy. (e) Fit a cubic model, and test for the significance of the cubic term using 0.05.