Impact of vitamin B supplement. In the Journal of Nutrition (July 1995), University of Georgia researchers examined the impact of a vitamin B supplement (nicotinamide) on the kidney. The experimental ‘‘subjects'' were 28 Zucker rats-a species that tends to develop kidney problems. Half of the rats were classified as obese and half as lean.
Within each group, half were randomly assigned to receive a vitamin B-supplemented diet and half were not. Thus, a 2 × 2 factorial experiment was conducted with seven rats assigned to each of the four combinations of size (lean or obese) and diet (supplemental or not). One of the response variables measured was weight (in grams) of the kidney at the end of a 20-week feeding period. The data (simulated from summary information provided in the journal article) are shown in the table.
(a) Conduct an analysis of variance on the data. Summarize the results in an ANOVA table.
(b) Conduct the appropriate ANOVA F-tests at α = .01. Interpret the results.