voodoochild wrote:
Each bank in the town of La Rinconada has only a single set of locking doors at its entrance. In the town of Inverness, on the other hand, the entrances to nearly all banks are equipped with two sets of locking doors, operated by a mechanism that allows only one set of doors to be open at a time. It is clear, then, that banks in Inverness experience more robbery attempts than do those in La Rinconada, and have thus adopted the extra doors as a security measure.
Which of the following, if true, most weakens the argument above?
a) Last year the number of bank robberies in La Rinconada was almost one-half greater than the corresponding figure for the previous year.
b) Inverness is known for its harsh winters, while the climate of La Rinconada is quite temperate year-round.
c) The mechanism of the double doors used by banks in Inverness allows bank security personnel to lock the doors remotely.
d) Bank robbery attempts are typically unsuccessful, and, even when the robbers do manage to escape with stolen money, the sum is usually quite small.
e) Inverness has almost twice as many police officers per capita as does La Rinconada.
Why is A) not a weakener? If the # of bank robberies in La Rin is > that in Inverness, the security is obviously out of question.
I'm responding to a PM on this one. I will start by saying the correct answer will be more logical to people who live in climates where double doors are used to maintain inside temperatures, but you can get to the answer by working through your CR process.
Assumptions fill in the logical gaps between premises and conclusions. If you want to weaken an argument you need to attack an assumption. In this question the premises state that Inverness has double doors and La Rinconada has single doors. The conclusion states that the double doors were for robbery prevention against Inverness' higher robbery rate. How do we get from double doors to robbery? We are assuming that the double doors are a method for preventing robbery (this is the logical gap between the premises and the conclusion).
Answer choices A, D, and E can quickly be eliminated for irrelevance to the issue of doors and robbery prevention. Since the correct answer is B, let's first analyze C. Choice C states that the double doors can be locked remotely. That seems to strengthen the assumption that the double doors are for robbery prevention. That choice feels very relevant to the argument but it's relevant in the wrong direction. We are trying to weaken the argument so we have to attack the assumption that doors are for robbery prevention, not strengthen it.
That only leaves us with choice B. Again, I will admit this requires a bit of a mental stretch for some, but can you think of the impact that climate has on door selection or use? Sure, when it's warm I sometimes leave my door open, but when it's cold or stormy I will absolutely close my door. This choice does provide information to suggest that the double doors may not have been installed for robbery prevention and instead as a protection against climate.
Don't be too quick to call some answer choices like this one out of scope. These questions can introduce new information not previously stated in the argument. The question is whether that new information attacks an assumption and therefore weakens the argument.
KW