In an article in Public Roads (1983), Bissell, Pilkington, Mason, and Woods study bridge safety (measured in accident rates per 100 million vehicles) and the difference between the width of the bridge and the width of the roadway approach (road plus shoulder):

The MINITAB output of a simple linear regression analysis relating accident to width difference is as follows:

Using the MINITAB output
a. Identify and interpret the least squares point estimate of the slope of the simple linear regression model.
b. Identify and interpret the p-value for testing H0: β1 = 0 versus Ha: β1 ‰  0.
c. Identify and interpret r2.

Transcribed Image Text:

WidthDiff.6 Accident -4 103 8 10 12 127 4 6 31 120 87 72 58 20 The regression equation is Accident Rate = 74.7-6.44 widthDif Predictor Constant WidthDif Coef 74.727 -6.4424 SE Coef 1.904 0.2938 39.25 -21.93 0.000 0.000 S. 5.33627 R-Sq 98.4% R-Sq (adj ) 98.2% # # Analysis of Variance Source Regression Residual Error Total DF 1 sS 13697 228 13924 MS 13697 28 480.99 0.000 9