Example 16. One-Way Fixed-Effects ANOVA Model: Veneer Data

Four specimens of each of five brands of a synthetic wood veneer material are subjected to a friction test. A measure of wear is determined for each specimen. All tests are made on the same machine in completely random order. The five brands are ACME, CHAMP, AJAX, TUFFY, and XTRA. The brands ACME and AJAX are produced by a U.S. company A-line while CHAMP is produced by a U.S. company C-line. TUFFY and XTRA are produced by a foreign company. The data is shown below.

Source: Littell, R.C., Freund, R.J., and Spector, P.C. (1991). SAS System for Linear Models. SAS Institute Inc.

Table 16: Veneer Data

Questions:

1. Is there evidence to reject the hypothesis that the brand means are the same? If yes, can we say which of the five brands caused the significance?
   
   
2. What are the assumptions that we made?
   
   
3. Compare
   1. means for the U.S. companies with the means for the foreign companies,
   2. means for the two U.S. companies with each other,
   3. means for the two A-line companies.
   
   
   

Keywords: Balanced one-way ANOVA, F-test, contrast, multiple comparisons