48. The tensile strength of a certain synthetic fiber is thought to be related to x1, the percentage of cotton in the fiber, and x2, the drying time of the fiber. A test of 10 pieces of fiber produced under different conditions yielded the following results.

(a) Fit a multiple regression equation.

(b) Determine a 90 percent confidence interval for the mean tensile strength of a synthetic fiber having 21 percent cotton whose drying time is 3.6.

Transcribed Image Text:

Y = Tensile Strength 213 x1 = Percentage of Cotton 13 x2 = Drying Time 2.1 220 15 2.3 216 14 2.2 225 18 2.5 235 19 3.2 218 20 2.4 239 22 3.4 243 17 4.1 233 16 4.0 240 18 4.3