An engineer suspects that the surface finish of metal parts is influenced by the type of paint used and the drying time. She selects two drying times—20 and 30 minutes—and uses two types of paint. Three parts are tested with each combination of paint type and drying time. The data are as follows

(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:

Drying Time (min) Paint 20 30 1 74 78 64 85 50 92 2 92 66 86 45 68 85