GMAT : Analysis of An Argument

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An Argument

82. The following appeared in the editorial section of a newspaper in the country of West Cambria.

The practice of officially changing speed limits on the highways - whether by increasing or decreasing them - is a dangerous one. Consider what happened over the past decade whenever neighbouring East Cambria changed its speed limits. An average of 3 percent more automobile accidents occurred during the week following the change than had occurred during the week preceding it - even when the speed limit was lowered. This statistic shows that the change in speed limit adversely affected the alertness of drivers.


Discuss how well reasoned you find this argument. In your discussion be sure to analyze the line of reasoning and the use of evidence in the argument. For example, you may need to consider what questionable assumptions underline the thinking and what alternative explanations or counterexamples might weaken the conclusion. You can also discuss what sort of evidence would strengthen or refute the argument, what changes in the argument would make it more logically sound and what, if anything, would help you better evaluate in conclusion.


This editorial asserts that West Cambria should not change its highway speed limits because such changes adversely affect driver alertness and are therefore dangerous. To support this claim, the editorial cites statistics indicating that whenever East Cambria changed its speed limits, an average of 3 percent more automobile accidents occurred during the week after the change than during the week preceding it, even when the speed limit was lowered.

As it stands, this argument suffers from three critical flaws.

First, it is unlikely that the brief one-week periods under comparison are representative of longer time periods. A difference of only 3 percent during one particular week can easily be accounted for by other factors, such as heavy holiday traffic or bad weather or by problems with reporting or sampling. Had the editorial indicated that several speed-limit changes in East Cambria contributed to the statistic, the argument would be more convincing. But for all we know, the statistic is based on only one such change. In any event, a one-week period is too brief to be representative because it is likely that accidents will occur more frequently immediately following the change, while people adjust to the new limit than over the longer term when drivers have become accustomed to the change.

Secondly, the editorial fails to acknowledge possible differences in the types of accidents occurring before and after the change. It is possible that the accidents during the week before the change all involved fatalities, while those during the week after the change were minor fender-benders. If so, even though 3 percent more accidents occurred after the change, the author's argument that changing the speed limit increases danger for drivers would be seriously weakened.

Thirdly, the editorial fails to take into account possible differences between East and West Cambria that are relevant to how drivers react to speed-limit changes. Factors such as the condition of roads, average age and typical driving habits of residents and weather patterns would probably affect how well or how quickly drivers adapt to speed-limit changes. Thus, changing speed limits in East Cambria might be more dangerous than changing them in West Cambria.

In conclusion, the statistical evidence cited to support the argument is insignificant and probably unrepresentative. To better evaluate the argument, we need to know how many speed-limit changes contributed to the statistic and when the speed-limit changes were made. Finally, to strengthen the argument the author should show that East and West Cambria would be similarly affected by speed-limit changes.

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