21. Wrinkle recovery angle and tensile strength are the two most important characteristics for evaluating the performance of crosslinked cotton fabric. An increase in the degree of crosslinking, as determined by ester carboxyl band absorbence, improves the wrinkle resistance of the fabric (at the expense of reducing mechanical strength). The accompanying data on x
absorbance and y
wrinkle resistance angle was read from a graph in the paper “Predicting the Performance of Durable Press Finished Cotton Fabric with Infrared Spectroscopy” (Textile Res. J., 1999: 145–151)

Here is regression output from MINITAB:

Predictor Coef SE Coef T P Constant 321.878 2.483 129.64 0.000 absorb 156.711 6.464 24.24 0.000 S = 3.60498 R-Sq = 98.5% R-Sq(adj) = 98.3%

Source DF SS MS F P Regression 1 7639.0 7639.0 587.81 0.000 Residual Error 9 117.0 13.0 Total 10 7756.0

a. Does the simple linear regression model appear to be appropriate? Explain.

b. What wrinkle resistance angle would you predict for a fabric specimen having an absorbance of .300?

c. What would be the estimate of expected wrinkle resistence angle when absorbance is .300?