3. In Chicago, a sample of 134 parcel carries reported that 8 had been bitten by an animal in the month of March. In a sample of 158 parcel carriers in Miami, 13 had received animal bites in March. a. Construct a 98% confidence interval for the true difference in proportions for these two cities. Provide the form your interval takes, along with the values required for this level of confidence. b. What information does your interval provide about the difference in proportions? c. What else might explain the difference? (Hint: Is there a confounding variable?)