Swim at your own risk Recent research suggests that exposure to disinfection by-products (DBPs) in swimming pools may increase the risk of some cancers.38 A study was conducted to determine whether exposure to DBPs in pool water increased toxic biomarkers. A random sample of adults was obtained and the concentration of four trihalomethanes (THMs, in μ/m3) in exhaled breath was measured before and one hour after swimming. Assume that the distribution of pairwise differences is continuous and symmetric. Use the Wilcoxon signed-rank test with a = 0.05 to determine whether there is any evidence that the median THM concentration is greater after swimming.