Problem 18E

An article in Biotechnology Progress (2001, Vol. 17, pp. 366–368) reported on an experiment to investigate and optimize nisin extraction in aqueous two-phase systems (ATPS). The nisin recovery was the dependent variable (y). The two regressor variables were concentration (%) of PEG 4000 (denoted as x1 and concentration (%) of Na2SO4 (denoted as x2). The data are in Table E12-10.

(a) Fit a multiple linear regression model to these data.

(b) Estimate σ2 and the standard errors of the regression coefficients.

(c) Use the model to predict the nisin recovery when x1 = 14.5 and x2 = 12.5.

9-26 & 9-28 NOTES Page 1 Household Transaction Model Public Sector Private (governmen Volunteer Sector Sector (business) FAMILY/ HOUSEHOL D Interhousehold (HH) Intrahouseho ld (between 2 homes) (within the