A multiple regression analysis was carried out to relate y

Chapter 13, Problem 13.77

(choose chapter or problem)

A multiple regression analysis was carried out to relate y tensile strength of a synthetic-fiber specimen to the variables x1 percent cotton and x2 drying time. The data set consisted of n 12 observations. a. The estimated coefficients were 0 180.00, 1 1.000, and 2 10.500. Calculate a point estimate of the expected tensile strength when percent cotton 15 and drying time 3.5. b. Sums of squares were SST 1210.30 and SSE 117.40. What proportion of observed variation in tensile strength can be attributed to the model relationship? c. Use the information in part (b) to decide whether the model with variables x1 and x2 specifies a useful relationship. d. The estimated standard deviation of 0 1x1 2x2 when x1 18 and x2 3.0 was 1.20. Calculate a 95% PI for tensile strength of a fabric specimen for which x1 18 and x2 3.0.