2. (20 points total) In this class, we discussed the 1950's nationwide Salk vaccine clinical trial on school children. The following contingency table shows the results of the clinical trial and whether the children who received the vaccine contracted Polio or not. ' Polio No Polio l Total Treatment 1 56 199,944 1 200,000 Control 1 142 199,858 1 200,000 Total 1 198 399,802 1 400,000 (a) (10 points) Perform a X2 test at the 0.05 level of signicance to test whether there is an association between receiving the vaccine and contracting Polio. Be sure to follow the 8 steps we have previously outlined for hypothesis tests. (b) (5 points) Calculate and interpret a 95% condence interval for the true odds ratio of Polio for children who received the Salk vaccine compared to those in the placebo group