In a study, researchers repeatedly measured the thickness of a specific artery in each of thousands of volunteers over several...
GMAT Critical Reasoning : (CR) Questions
In a study, researchers repeatedly measured the thickness of a specific artery in each of thousands of volunteers over several years. The researchers found during the study that the artery became thicker more quickly in individuals who lived in cities with significant air pollution. Since thick arterial walls are associated with heart disease, the researchers concluded that exposure to significant urban air pollution contributes to heart disease.
In order to assess the force of the researchers' evidence for their conclusion, it would be most helpful to know whether
Passage Analysis:
| Text from Passage | Analysis |
| In a study, researchers repeatedly measured the thickness of a specific artery in each of thousands of volunteers over several years. |
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| The researchers found during the study that the artery became thicker more quickly in individuals who lived in cities with significant air pollution. |
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| Since thick arterial walls are associated with heart disease, the researchers concluded that exposure to significant urban air pollution contributes to heart disease. |
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Argument Flow:
The argument starts with describing a long-term study design, then presents the key finding that pollution correlates with faster artery thickening, and finally uses medical knowledge about thick arteries to conclude that pollution contributes to heart disease.
Main Conclusion:
Exposure to significant urban air pollution contributes to heart disease.
Logical Structure:
The researchers use a two-step logical chain: (1) their study shows pollution leads to thicker arteries, and (2) existing medical knowledge shows thick arteries are associated with heart disease, therefore (3) pollution contributes to heart disease. This creates a cause-and-effect argument linking pollution → thick arteries → heart disease.
Prethinking:
Question type:
Evaluate - We need to find what additional information would help us assess how strong or weak the researchers' evidence is for their conclusion that air pollution contributes to heart disease
Precision of Claims
The study found a correlation between living in polluted cities and faster artery thickening. The conclusion makes a causal claim that pollution contributes to heart disease based on this correlation plus the fact that thick arteries are associated with heart disease
Strategy
For evaluate questions, we need to think of key assumptions the argument makes, then create scenarios that would either strengthen or weaken the conclusion when we know whether they're true or false. The main logical gap here is jumping from correlation to causation - just because people in polluted cities had thicker arteries doesn't necessarily mean pollution caused it. We should think about alternative explanations and what information would help us rule them in or out
This asks whether any volunteers with thicker arteries lived in non-polluted areas. While this might provide some comparative information, it doesn't directly help us assess whether pollution is actually causing the artery thickening in polluted cities. Even if some people in clean areas also had thick arteries, that wouldn't tell us much about the pollution-artery relationship since there could be many other causes of artery thickening.
This asks whether the specific artery studied is typical of arteries in general. This is about the generalizability of the findings to other arteries, but it doesn't help us evaluate whether the evidence actually supports the causal claim about pollution causing heart disease. The strength of the causal argument remains the same regardless of whether this artery is typical.
This asks about factors that contribute to heart disease without affecting artery thickness. This is somewhat relevant but doesn't directly address the key issue of whether pollution is actually causing the observed artery thickening. It's more about alternative pathways to heart disease rather than alternative explanations for the artery findings.
This asks whether people with the thickest arteries at the end also started with thick arteries. This addresses whether the study measured actual change over time versus pre-existing differences, which is important for the study design but doesn't directly help evaluate the causal claim about pollution.
This directly targets the main logical gap by asking whether other environmental factors in polluted cities might be causing the artery thickening instead of pollution itself. If other factors are responsible, this would significantly weaken the conclusion. If pollution is the only relevant factor, this would strengthen the conclusion. This information is most helpful for assessing the force of the evidence.