An experiment is revealed in Myers and Montgomery (2002) in whom optimum conditions are sought storing bovine semen to obtain maximum survival. The variables are percent sodium citrate, percent glycerol, glycerol, and equilibration time in hours. The response is percent survival of the motile spermatozoa. The natural levels are found in the above reference. Below are the data with coded levels for the factorial portion of the design and the center runs.(a) Fit a linear regression model to the data and determine which linear and interaction terms are significant. Assume that the x1x2x3 interaction is negligible.(b) Test for quadratic lack of fit andcomment.

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21, Percent Sodium Percent Equilibration Citrate Glycerol Time Survival 57 -1 -1 - 1 40 19 40 54 41 21 43 -1 -1 --1 - 1 - 1 -1 63 61