An article in the Journal of Testing and Evaluation

(Vol. 16, no. 2, pp. 508–515) investigated the effects of cyclic loading and environmental conditions on fatigue crack growth at a constant 22 MPa stress for a particular material. The data from this experiment are shown below (the response is crack growth rate):

Environment Frequency Air H2O Salt H2O 2.29 2.06 1.90 10 2.47 2.05 1.93 2.48 2.23 1.75 2.12 2.03 2.06 2.65 3.20 3.10 1 2.68 3.18 3.24 2.06 3.96 3.98 2.38 3.64 3.24 2.24 11.00 9.96 0.1 2.71 11.00 10.01 2.81 9.06 9.36 2.08 11.30 10.40

(a) Analyze the data from this experiment (use ???? = 0.05).

(b) Analyze the residuals.

(c) Repeat the analyses from parts

(a) and

(b) using ln (y)

as the response. Comment on the results.