Reports Are Available on a Study in Which Various Measurements

Reports are available 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. 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 l.05. $$\begin{array} { l c c c c c c c c } \hline \text { Unexposed } & 8 & 11 & 12 & 14 & 20 & 43 & 111 & \\\hline \text { Exposed } & 35 & 56 & 83 & 92 & 128 & 150 & 176 & 208 \\\hline\end{array}$$