A university study reported that between 1975 and 1983 the length of the average workweek in a certain country increa...

Irina on September 26, 2019

@chris_va,

The argument is telling us that a government study found that the average workweek became shorter, and a university study found that the average workweek became longer. Then the argument tells us that the studies used different methods, and not the basis of this fact alone concludes that there is no need to look for further explanation of the difference in the results. The argument assumes that because studies use different methods they must necessarily produce different results. The correct answer (D) challenges this assumption, saying what if two studies use different methods can yield identical results, then the conclusion is flawed because we must look into other causes of these studies reaching the opposite conclusions.

To answer your question, (D) only refers to two different methods of investigation, not two studies, meaning the argument never challenges the fact that these two studies produced different results - otherwise, it would contradict the premises as you correctly pointed out, but only argues WHY these two studies produced different results. The argument tells us that the fact that they used different methods of investigation is enough to dismiss any other reasons, and (D) points out that the argument fails to consider that as a general principle, two different methods of investigation could yield identical results.

Let me know if you have any further questions.