Police chief: During my tenure as chief, crime in this city has fallen

Please explain why B is wrong. It tells at the start of the tenure the rate was loower than it is now. So the policy taken by the chief was not effective

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because it has to assume that the crime condition (e.g. proportion of population with tendency to commit crime) is the same between now and several decades ago.

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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Answer choice (D) does not seem to make much sense. Let's say that in the entire country 100 crimes are committed. Let's say, in the city, there are 20 crimes. During police's tenure, the crime rates fell by 20% (so, now there are 16 crimes committed in the city). The city's overall crime rate fell by 30% (so, now overall there are 70 crimes committed, out of which 16 crimes are committed in the city). From this, how can we say that there is an alternate cause at play and not the police's strategy in crime reduction?

Kindly help resolve!

Pre-thinking:

Conclusion: The fall in crime in the city is due to the chief's policing strategy.

Premise on which it is based:

i) Policing strategy focused on targetting areas with high crime rates.
ii) Crime in the city fell 20% during the chief's tenure.

In order to weaken the conclusion, we are looking for one of the following:

i) Alternate reason for fall in crime.
ii) Reverse causality ie; it is not the strategy which caused the reduction in crime but the reduction in crime which caused the strategy.
iii) Correlation ie; a third variable causing both the reduction in crime as well as the policing strategy.

Let us examine the answer options.

(A) The crime rate in the police chief's city is still significantly higher than in many other cities. The conclusion has nothing to do with crime rates in other cities. Irrelevant. Eliminate.

(B) The crime rate in the police chief's city is higher now than it was several decades before the chief's tenure began. Does not weaken the conclusion as we are only concerned with happened during the chief's tenure. What happened several years before the chief began his/her tenure is not relevant. Eliminate.

(C) The crime rate in the police chief's city fell significantly during the first few years of the chief's tenure, then it leveled off. Does not weaken the conclusion. The fall in the initial years could still have been due to the policing strategy. Eliminate.

(D) The crime rate in the country as a whole fell by about 30 percent during the police chief's tenure. Correct answer. This provides a possible alternate reason for the fall in crime in the city - it could be due to a fall in crime in the country as a whole and not due to policing strategy.

(E) The variation in crime rates between different areas of the city is smaller in the police chief's city than in many other cities. The conclusion does not address crime within the city divided by the areas. Irrelevant. Eliminate.

Hope this helps.

Hi Sagar

Option (D) tells us that crime in the whole country fell by 30% during the period of the chief's tenure. This fall must be due to some cause (for eg: improving employment opportunities in the country). Let us call that cause X.

We know that X is acting across the country as a whole. Therefore, it is possible that X is also acting within the "city" mentioned in the stimulus. We also know that the effect of X is to cause a fall in crime. Therefore, it is possible that it is X that caused the fall in crime in the city and not the policing strategy. It is not certain but it is a possiblity. That is sufficient for us to consider this as a potential weakener.

There is no other answer option that provides a better weakener and the question states, "Which one of the following, if true, most calls into question...". Therefore, of the given options, (D) is the best possible answer.

Hope this helps.