Question

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.

Answer 1

Answer:

f. Both C and D

Explanation:

Sounding an alarm warning that calls for the immediate decrease in the amount of chlorine used to treat drinking water, based on the result of the experiment is a very sound conclusion. First of all there exist a strong positive correlation of r = 0.79, which is close to 1. This means that the result of the experiment indicates that the higher the chlorine level in drinking water, the higher the rate of cancer incidence. Also, the experiment was carried out in 5 US cities, reducing the possibility of error due to a local factor. So, the conclusion is a very sound conclusion based on the experimental procedure, and the analysis of the result.