Answer
a) $90\%$
b) The claim should be accepted.
c) The p-value and critical value methods should be equal, while the newly-learned confidence interval method will be different.
Work Step by Step
a) We want a $0.05$ significance level, so our confidence level should be $90\%$.
b) We can see that the whole confidence interval is within the set of negative numbers. Hence we can see that set $p_1$ yields a lower risk of polio, meaning that the claim should be accepted.
c) The p-value and critical value methods, which we learned in previous chapters, should be equal, while the newly-learned confidence interval method will be different.
