26. The determination of the shear strength of spot welds is relatively difficult, whereas measuring the weld diameter of spot welds is relatively simple. As a result, it would be advantageous if shear strength could be predicted from a measurement of weld diameter. The data are as follows:

(a) Draw a scatter diagram.

(b) Find the least squares estimates of the regression coefficients

(c) Test the hypothesis that the slope of the regression line is equal to 1 at the .05 level significance.

(d) Estimate the expected value of shear strength when the weld diameter is .2500.

(e) Find a prediction interval such that, with 95 percent confidence, the value of shear strength corresponding to a weld diameter of .2250 inch will be contained in it.
(f ) Plot the standardized residuals.
(g) Does the plot in part

(f) support the assumptions of the model?

Transcribed Image Text:

Shear Strength (psi) 370 780 Weld Diameter (.0001 in.) 400 800 1,210 1,250 1,560 1,600 1,980 2,000 2,450 2,500 3,070 3,100 3,550 3,600 3.940 4,000 3,950 4,000