In a study to examine the utility of using ammonia gas to sanitize animal feeds, researchers inoculated corn silage with a strain of Salmonella. Next, two petri dishes of 5 g of contaminated feed were exposed to concentrated anhydrous ammonia gas and two control petri dishes of 5 g of contaminated feed were not treated with the gas. This experiment was repeated twice, for a total of three trials, as only two petri dishes could be placed in the pressurized gas chamber at any given time. Twenty-four hours after inoculation and gassing, the number of bacterial colonies (colony forming units or cfu) on each dish were counted. Because the data were highly skewed, the log(cfu) was analyzed.43
(a) Identify the blocking, treatment, and response variables in this problem.
(b) Complete the following ANOVA table for this blocked analysis.

(c) Using the complete table from part (b), is there evidence that the ammonia gas treatment affects the contamination level (i.e., mean log cfu)? Use α = 0.05.
(d) Do the preceding analysis and information allow you to infer that ammonia reduces contamination? If not, what other information would be necessary to make such a claim?

df SS MS Fratio Between treatments 11.14 .141 7.107 Between trials 2 3.61 Within groups Total 11 6036