13.1. The data given below are for thicknesses in 0.00001 in.

of nonmagnetic coatings of galvanized zinc on 11 pieces of iron and steel. The destructive (stripping) thickness is y; the nondestructive (magnetic) thickness is x:

x 105 120 85 121 115 127 630 155 250 310 443 y 116 132 104 139 114 129 720 174 312 338 465 We find n¼11, P x¼2461, P y¼2743, P x2 P ¼852,419, y2¼1,067,143, P xy¼952,517.

a. Plot a scatter diagram and comment.

b. Find r, bo, b1 and sy.x, write the estimation equation and draw it on the scatter diagram.

c. Is r significant?

d. Estimate y, if x¼150.