Cause and Effect type Conclusion.
There is an observed event: the crime has fallen 20% during the police chief’s tenure.
The Conclusion? The cause for this 20% decrease is the tactics employed by the police chief and the strategy of focusing on the areas with the most crime.
1 way to weaken a cause and effect conclusion is to provide evidence that suggests there is an alternative explanation to why the observed 20% decrease in crime occurred. The author is assuming that his stated cause (the tactics and focus on the most crime ridden areas) is the sole driving force behind the effect.
D shows that everywhere in the nation crime as fallen by 30%. In a weaken q, we just want to make it a little less likely that the conclusion is true. The information should cast doubt on whether the conclusion is actually true.
If all over the nation there has been a significant decrease in crime, this new info. tends to suggest that it might not be the police chief’s tactics and strategies that is the driving cause behind the 20% decrease in crime in his city. There may be some alternative causation on the National level that is at play.
Since this info gives us enough of a reason to doubt the truthfulness and validity of his conclusion, the argument is weakened.
D
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