Cornell (1988) considered data on scaled thickness values for five formulations of vinyl designed for use in automobile seat covers. Eight groups of material were prepared.

The production process was then set up and the five formulations run with the first group. The production process was then reset and another group of five was run. In all, the production process was set eight times and a group of five formulations was run with each setting. The data are displayed in Table 17.17.

(a) From the information given, identify the design for this experiment and give an appropriate model. List all the assumptions made in the model.

(b) Analyze the data. Give an appropriate analysis of variance table. Examine appropriate contrasts using the Bonferroni method with an α of about .05.

(c) Check the assumptions of the model and adjust the analysis appropriately.