Question

Experimental studies of cancer often use strains of animals that have a naturally high incidence of tumors. In one such experiment, tumor prone mice were kept in a sterile environment with one group of mice maintained entirely germ free and the other group of mice exposed to the intestinal bacterium Eschericbia coli. The accompanying table shows the incidence of liver tumors. Let and  represent the probabilities of liver tumors under the sterile and the E. coli conditions, respectively.

	Sterile	E. coli
Liver Tumor	19	8
No Tumor	30	5

Conduct a hypothesis test at the 0.01 significance level to test whether there is a difference in the probability of liver tumor under E.coli versus control conditions. Find the absolute value of the test statistic using prop.test() in R.

Answer 1