A year ago the government reduced the highway speed limit, and in the year since, there have been significantly fewer...

David on October 8, 2015

E appears to be invalid?

The passage does not discuss the number of fatalities. It only speaks to a significant reduction in fatalities than the previous year. E states that the number of fatalities was not abnormally high to begin with, however, the passage only mentions that there was a significant reduction. D seems to weaken because it speaks to enforcement reducing the fatalities not the reduction of the highway speed limit.

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Melody on October 15, 2015

We are faced with a cause and effect weaken question. The argument reasons that speed limit reduction can reduce traffic fatalities because a year ago the government reduced the highway speed limit, and in the year since, there have been significantly fewer highway fatalities than there were in the previous year. The passage does discuss the number of fatalities by stating that there have been fewer fatalities than there were in the previous year; remember that "fewer" is an adjective used with a countable noun.

How do we weaken a cause and effect argument? We must show that either Y caused X (as opposed to X caused Y), or some third factor Z actually caused Y.

Answer choice (D) does not actually weaken the argument. If the new speed limit, i.e. the newly reduced speed limit, was more strictly enforced, then we are merely making sure that the new speed limit is actually creating the effect that we see. If it is true that the new speed limit is even better enforced the previously higher one, then it is true that the reduced speed limits, which are now being enforced, play a part in causing reduced traffic fatalities.

Answer choice (E), on the other hand, brings about the possibility that Z caused Y, i.e. if the previous year had an abnormally high amount of traffic fatalities, then the number of traffic fatalities stabilizing back down to their normal amount may not necessarily be due to the reduced speed limits; it could merely be due to the fact that whatever was causing the abnormally high fatality rate is no longer present.

Thus, it is not necessarily true that the reduced speed limit caused the reduced number in traffic fatalities.

Hope that helps! Please let us know if you have any other questions.