A research team is interested in the difference between serum uric acid levels in patients with and

without Downs syndrome. In a large hospital for the treatment of the men- tally retarded, a sample

of 12 individuals with Downs syndrome yielded a mean of x1 = 4:5 mg> 100 ml. In a general

hospital a sample of 15 normal individuals of the same age and sex were found to have a mean value

of x2 = 3.5. If it is reasonable to assume that the two populations of values are normally distributed

with variances equal to 1 and 1.5, find the 95 percent confidence interval for 1 ???? 2.