An article in the Journal of Pharmaceutical Sciences (Vol. 80, 1991) presents data on the mole fraction solubility of a solute at a constant temperature. Also measured are the dispersion x1, and...

An article in the Journal of Pharmaceutical Sciences (Vol. 80, 1991) presents data on the mole fraction solubility of a solute at a constant temperature. Also measured are the dispersion x1, and dipolar and hydrogen bonding solubility parameters x2, and x3. A portion of the data is shown in the table below. In the model, y is the negative logarithm of the mole fraction. Fit the model Vi = 00 + 0Xli + 02X2i + ß3x3i + €i for I = 1, 2, …, 20.

(a) Test H0: ß1 = ß2 = 03 = 0.

(b) Plot studentized residuals against x1, x2, and x3 (three plots). Comment

(c) Consider two additional models that are competitors to the models above. With these three models use PRESS and Cp to arrive at the best among the three.