Suppose an ecologic study comparing chlorine levels in drinking water and cancer rates in 5 US cities shows a strong positive correlation (r = 0.793). In other words, cities with higher levels of chlorine in the drinking water supply had higher rates of cancer incidence compared to cities with lower levels of chlorine in the drinking water supply. Based on these results, the authors call for an immediate decrease in the amounts of chlorine used to treat drinking water. Is this a sound conclusion? a. No, because chlorine is not a carcinogen.
b. No, because the ecologic fallacy may be explaining the result.
c. Yes, because the correlation is strong.
d. Yes, because the data are from a large, multi-city study.
e. Both A and B.
f. Both C and D.