An article in the Journal of Testing and Evaluation

(Vol. 16, No. 6, 1988, pp. 508–515) investigated the effects of cyclic loading frequency and environmental conditions on fatigue crack growth at a constant 22 MPa stress for a particular material. Some of the data from the experiment are shown here. The response variable is fatigue crack growth rate.

(a) Compute the estimates of the effects and their standard errors for this design.

(b) Construct two-factor interaction plots and comment on the interaction of the factors.

(c) Use the t ratio to determine the significance of each effect with 0.05. Comment on your findings.

(d) Compute an approximate 95% CI for each effect.
Compare your results with those in part

(c) and comment.

(e) Perform an analysis of variance of the appropriate regression model for this design. Include in your analysis hypothesis tests for each coefficient, as well as residual analysis. State your final conclusions about the adequacy of the model. Compare your results to part

(c) and comment.

Transcribed Image Text:

Frequency Environment HO Salt HO 2.06 1.90 2.05 1.93 10 2.23 1.75 2.03 2.06 3.20 3.10 3.18 3.24 1 3.96 3.98 3.64 3.24