8.64 Vaccine for Diarrhea A vaccine to prevent severe rotavirus gastroenteritis (diarrhea) was given to African children within the first year of life as part of a drug study. The study reported that of the 3298 children randomly assigned the vaccine, 63 got the virus, Of the 1641 children randomly assigned the placebo, 80 got the virus. (Source: Madhi et al., Effect of human rotavirus vaccine on severe diarrhea in African infants, New England Journal of Medicine, vol. 362: 289-298, January 28, 2010) a. Find the sample percentage of children who caught the virus in each group. Is the sample percent lower for the vaccine group, as investiga- tors hoped? b. Determine whether the vaccine is effective in reducing the chance of catching the virus, using a significance level of 0.05. Steps I and 2 of the hypothesis-testing procedure are given. Complete the question by doing steps 3 and 4. Step 1: Ho: P. = Pp (p. is the proportion that got the virus among those who took the vaccine, and po is the proportion that got the virus among those who took the placebo.) H_ P.