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A research team is interested in the difference between serum uric acid levels in patients with and without Down's syndrome. In a large hospital for the treatment of the mentally retarded; a sample of 12 individuals with Down's syndrome yielded a mean of 4.5 mg/i 00 ml. in a general hospital a sample of 15 normal individuals ofthe same age and sex were found to have a mean value of 3,4 mg/'l 00 ml, If it is reasonable to assume that the two populations of values are normally distributed with variances equal to I and 15, nd the 95 percent condence interval, (3 decimal places) upper limit =