6. In the paper "The Racial Crossover in Comorbidity, Disability and Mortality" (Demography, Vol. 37(3), pp. 267-283), N. Johnson investigated the proportion of elderly white and African-American over the age of 70. Of the 4,989 white elderly surveyed, 529 had at least one stroke whereas 103 of the 906 African-American elderly has at least one stoke. a) Construct a 90% confidence interval for the true difference between these proportions. (6 pts) b) Use your interval to make a decision for the following hypotheses. Provide an explanation for your decision and include the a level related to your interval. The subscripts "AA" and "W" are for the African-American and white elderly, respectively. (3 pts) Ho: PAA = PW H1 : PAA # PW