The findings of recent research indicate that prolonged exposure...

This is a “Useful to Evaluate” question, which borrows many tactics from traditional Strengthen/Weaken questions. (The leverage phrase in the question stem, “which… would be most helpful in evaluating…” clearly indicates this question type.) With Useful to Evaluate questions, "Minding the Gap" is critical. The correct answer will either plug the gap (Strengthen) or explode the gap (Weaken). Trap answers will not address the logical gap.

The primary logical gap in this question is the disconnect between the data and the conclusion. While the data tells us that workers who spend 20+ hours in front of a computer monitor exhibit a 12% reduction in cognitive abilities after 15 years, we don’t know if that 12% reduction is actually caused by the exposure or if it might be caused by something else during those 15 years. (For example, what if most people who sit at a job for 15 years see a much greater decline in cognitive ability? A mere 12% reduction could actually show that sitting in front of computer monitors keep your brain relatively sharp! Alternatively, what if it isn’t the radiation that causes the decline; instead, sitting in one position for 15 years is what actually causes it?) We need to find the answer choice that addresses this gap in some way.

Answer choice A “moves the goalposts” on the reader, getting the reader to think that the reversibility (or permanency) of the damage matters. This introduces an emotional, human component to the story, but one that isn’t related to the logical gap. A is a trap answer.

Answer choice B traps those who misunderstand what the problem is asking. While questioning the 15-year period might be interesting if someone is evaluating the study as a whole, the question stem explicitly asks us to identify the question that can best help us evaluate the specific reasoning presented. Answer choice B does not address the logical gap between the data and the conclusion.

At first glance, answer choice C looks like it helps us to compare the rates of cognitive decline across a spectrum of various occupational tasks. However, answer choice C is a Yes/No question that doesn’t really help us much: if the answer is “No”, then it appears that occupational tasks might not determine cognitive decline. But if we answer “Yes”, then we only know that there is a relationship between occupational tasks and cognitive decline. We don’t know what that relationship is, and we have no data points to compare. Answer choice C gets us started, but is very weak.

Answer choice D doesn’t mind the logical gap. In fact, the problem states that the “average” cognitive decline was 12%. This data point implies that either (1) all of the participants somehow had the exact same 12% drop, or (2) some people were above and others were below the 12% average. That is how “average” works. It is very likely that the data was spread around the 12% average, so D tells us very little. And D certainly doesn’t address the lack of clear causal link between monitor exposure and cognitive decline.

Answer choice E gives us a strong comparative that can help us prove (or disprove) a potential causal link. The answer to the question in this answer choice would give us a measurable number against which we can compare the 12% cognitive decline. Whether the cognitive decline rate of the average worker is higher than, lower than, or equal to the measured 12% decline, such data could give us strong leverage to evaluate the reasoning in the argument. Answer choice E is the correct answer.