Question: In a random sample of 2,300 mortgages taken out in a certain region last year, 187 were adjustable-rate mortgages.
a. Give a point estimate of the proportion of all mortgages taken out in this region last year that were adjustable-rate mortgages.
b. Assuming that the sample is sufficiently large, construct a 99.9% confidence interval for the proportion of all mortgages taken out in this region last year that were adjustable-rate mortgages.