Noting that the number of crimes committed in a certain city had decre

GMATNinja

Can someone let me know why C is wrong?

I thought C weakens the argument since it implies that the crimes committed actually didn't decrease, but just phased out to suburban areas as a balloon effect.

I myself actually chose C but with C there remains a scope of a possibility that this balloon effect is actually a result of the Police program. With E, the scope of the previously-mentioned possibility gets diminished completely.

great question - chose E after ~2 mins

Got to the answer mainly by PoE but it also makes a lot of sense why E is the right choice here.

C is wrong because it refers to suburban areas outside the city, whereas the argument only refers to the city. thus, this answer choice is completely OOS.

Argument Type : Assumption + Weaken

Premise: the number of crimes decreased by 5.2%
Assumption: there is another reason for the decrease (ex. population change)
Conclusion: decrease is the result of an innovative police program

A: OOS, we are not interested in several other cities
B: Strengthen, if the method has changed, we could have doubt that the decrease is due to the changed method. However, since this option says the method did not change at all, it actually strengthens the conclusion rather than weaken.
C: Strengthen, since the conclusion has a limited scope saying that “ ~ put into effect in the city,” it has nothing to do with suburban areas. Furthermore, this can actually imply that because the police program did have an effect inside the city, criminals moved to suburban areas.
D: Strengthen, this actually implies that the number of crimes committed has decreased since in the past.
E: Correct. The decrease in the number of committed crimes was due to decreased population, not police program.

Noting that the number of crimes committed in a certain city had decreased in 1982 by 5.2 percent in comparison with 1981, the police chief of the city said, "We see here the result of the innovative police program put into effect in the city at the beginning of 1982."

Which of the following, if true, most seriously weakens the conclusion drawn by the police chief?

(A) Several cities that have recently increased spending for police programs experienced no decrease in crime in 1982, as compared with 1981.
Not relevant. The argument does not says about several cities.

(B) The number of crimes committed in the city is estimated, by the same method each year, from the number of crimes reported.
Opposite. This is strengthning the argument.

(C) The number of crimes committed in the suburban areas surrounding the city rose by about 5 percent in 1982 over the figure for 1981 and were nearly equal in number to those in the city in 1982.
Conclusion is crime decreased in 1982 by 5.2%

(D) The number of crimes committed in the city in 1982 was 10 percent higher than the number committed in 1972.
No comparison is required with 1972

(E) The size of the age-group most likely to commit crimes decreased considerably in the city in 1982, as against 1981, because of a declining birth rate.
This is in line with argument. The alternate reason for decrease in crime other than police mentioned.

(A) Several cities that have recently increased spending for police programs experienced no decrease in crime in 1982, as compared with 1981. -- We are not concerned with other cities since the claim is about a particular city. Eliminate. Out of scope.

(B) The number of crimes committed in the city is estimated, by the same method each year, from the number of crimes reported. -- Shell game. I kept it till last. Finally eliminated on the grounds of it being very ambiguous. If the reporting method is same, then we don't have any reasons to doubt that crimes are not being reported this year. Eliminate.

(C) The number of crimes committed in the suburban areas surrounding the city rose by about 5 percent in 1982 over the figure for 1981 and were nearly equal in number to those in the city in 1982. -- Out of scope since this choice talks about suburban areas when we are concerned with crime in the main city.

(D) The number of crimes committed in the city in 1982 was 10 percent higher than the number committed in 1972. -- Out of scope since our comparison is with 1971. Eliminate.

(E) The size of the age-group most likely to commit crimes decreased considerably in the city in 1982, as against 1981, because of a declining birth rate. -- Correct choice. This choice provides us an alternate cause for the claimed effect (drop in crime rate), thereby weakening the conclusion that the cause for the effect is increased policing.

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