The article “Measuring the Exposure of Infants to Tobacco Smoke” (New Engl. J. of Med.,...

The article “Measuring the Exposure of Infants to Tobacco Smoke” (New Engl. J. of Med., 1984: 1075–1078) reports on a study in which various measurements were taken both from a random sample of infants who had been exposed to household smoke and from a sample of unexposed infants. The accompanying data consists of observations on urinary concentration of cotanine, a major metabolite of nicotine (the values constitute a subset of the original data and were read from a plot that appeared in the article). Does the data suggest that true average cotanine level is higher in exposed infants than in unexposed infants by more than 25? Carry out a test at significance level .05.