A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors,...

GMAT Critical Reasoning : (CR) Questions

Source: Official Guide

Critical Reasoning

Assumption

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A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.

The conclusion drawn above depends on which of the following assumptions?

Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.

Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.

The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.

Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.

Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.

Solution

Passage Analysis:

Text from Passage	Analysis
A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles ticketed for exceeding the speed limit were equipped with them.	What it says: Only 3% of drivers have radar detectors, but 33% of speeding tickets go to drivers with radar detectors What it does: Sets up a surprising contrast between how few people have these devices vs how often they appear in speeding violations What it is: Study finding from a recent report Visualization: Total drivers: 100 people → 3 have radar detectors, 97 don't have them. Speeding tickets: 100 tickets → 33 go to people with radar detectors, 67 go to people without them
Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.	What it says: The author concludes that having a radar detector makes you more likely to speed regularly What it does: Draws a conclusion from the statistics we just saw, connecting the high percentage of tickets to regular speeding behavior What it is: Author's conclusion

Argument Flow:

The argument starts with statistical evidence showing a big mismatch - very few drivers have radar detectors (3%) but they make up a huge chunk of speeding tickets (33%). From this data, the author jumps to conclude that radar detector owners must be regular speeders.

Main Conclusion:

Drivers with radar detectors are more likely to speed regularly than drivers without them.

Logical Structure:

The author uses the disproportionate representation in speeding tickets (33% vs 3%) as evidence that radar detector users are more prone to regular speeding. However, this logic assumes that getting caught speeding reflects actual speeding behavior, ignoring other possible explanations for why radar detector users might get more tickets.

Prethinking:

Question type:

Assumption - We need to find what the author must believe to be true for their conclusion to hold. If we can falsify the conclusion while keeping all the given facts intact, we've found a gap that needs to be filled by an assumption.

Precision of Claims

The key claims involve frequency (regularly exceeding speed limits), proportions (3% vs 33%), and behavioral patterns (likelihood of speeding). The conclusion specifically claims radar detector owners are MORE LIKELY to speed REGULARLY than non-owners.

Strategy

Let's think about ways the conclusion could fall apart even with the given statistics. The author jumps from 'radar detector users get more tickets' to 'radar detector users speed more regularly.' What could break this logic? We need to find assumptions that bridge this gap between getting caught speeding and actually speeding more often.

Answer Choices Explained

Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.

This choice suggests radar detector users are LESS likely to get tickets than non-users. But wait - this contradicts the evidence we're given! The passage clearly states that 33% of tickets go to radar detector users who represent only 3% of drivers. This means they're actually MORE likely to get tickets, not less. So this assumption isn't needed for the argument - in fact, it goes against the premises.

Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.

This is the critical bridge we need! The author jumps from 'radar detector users get more tickets' to 'radar detector users speed more regularly.' But what if getting tickets doesn't actually correlate with regular speeding behavior? What if tickets are just random bad luck? The author MUST assume that people who get caught speeding actually do speed more regularly than those who don't get caught. Without this assumption, the whole argument crumbles because tickets wouldn't indicate actual speeding patterns.

The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.

This is talking about raw numbers - whether there were more total tickets than total radar detectors. But this doesn't matter for the argument! The conclusion is about likelihood and proportions (3% vs 33%), not absolute quantities. Whether there were 1,000 tickets or 10,000 tickets doesn't affect whether radar detector users are more prone to regular speeding.

Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.

This focuses on repeat offenders - whether some drivers got multiple tickets. While this might be interesting data, it's not necessary for the conclusion. The argument works whether each ticket represents a different driver or some drivers got multiple tickets. The key point is the proportion of tickets going to radar detector users, not the distribution pattern.

Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.

This compares Maryland drivers to other states. But the conclusion is specifically about the difference between radar detector users and non-users within Maryland, not about Maryland versus other states. Whether Maryland drivers speed more or less than drivers elsewhere is completely irrelevant to the internal comparison the author is making.

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