PrepTest 17 - Section 1 - Question 23 | Explanation & Discussion

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In a new police program, automobile owners in some neighborhoods whose cars are not normally driven between 1 . ████ ███ █ ████ ███ ███████ █ ███████ █████ ██ ███ ███████ ███████ ███ █████████ ██████ ██ ████ ███ ████ ██████ █████ █████ ██ █████ ███ ██████████ █████████ ███ █████ ████ ███ ████ ███████ ████ ██████ ██ ████ █████ ████ ███ ████ █████ ███ ████ ██ █████ ██████████████

Stimulus Summary

The stimulus tells us about a new program allowing car owners in certain neighborhoods who don't usually drive their cars between 1 a.m. and 5 a.m. to display a decal allowing police to stop their cars if they are found driving during those hours and check the drivers' licenses. We're told that this program has caused the theft rate for cars with such decals to decrease significantly compared to the previous rate for cars in those neighborhoods.

23.

If it is concluded from ███ ██████████ █████ ████ ██████████ █████ ███ ████ ███████ ██ ███ ████████ █████ ███ ██ ███ █████████ █████ ██ ██ ████ █████████ ██ ██████ ██ ██████████ ████ ███████████

Question Type

Evaluate

This question is tricky because there are two things going on. The first thing I noticed after reading the question stem is that the stimulus only tells us that the theft rate has gone down for a subset of automobile thefts: thefts involving these specific cars in these specific neighborhoods. For this to cause a decrease in automobile theft overall, we would need to know that there was no corresponding increase in some other subset of automobile thefts (e.g., thefts of cars not participating in this program) that would offset this decrease.

But if you look at the answer choices, you'll see that no answer choice gives us that information. So it's also important to notice that, beyond the part/whole issue, there is also a correlation/causation issue at play in this conclusion. The stimulus only tells us that this program is correlated with a decline in thefts. The conclusion in the question stem says that the program has caused this decline. To determine if this is true, we also need to know whether there are other potential causes for the decline.

Are owners who ███ ████████ ██████ ██ ████ ███ ███████ ██████ █████ ███████ ████████ ██ ███████ █████ ████ ███████ ██████

Correct. While this doesn't answer our initial question about the subset versus the larger set, this does help us answer the question of whether the program caused this particular decline. If the answer to (A) is yes, this suggests that there could be some other reason for the decline in thefts of these specific cars. Some other safety measure these owners are taking might be the real reason for the decline. If the answer to (A) is no, this increases our confidence that it is in fact this program that is pushing down thefts.

70%

In how many █████████████ ██ ███ ██████ ███████ ██████████

Incorrect. Even if the program was only operating in a few neighborhoods, the decrease in thefts as a result of this program could still reflect an overall decrease in automobile thefts if there was no increase in some other subset of thefts. Conversely, even if this program was operating in most or all neighborhoods, we would still need to know that there was no increase in other thefts that would offset the decrease. And knowing the answer to (B) also wouldn't help us determine if it was this program that actually caused the decrease.

Are cars in █████████████ ████ ███ ████████ █████████████ ██ ███ ███████ █████████ ██████ ██████ ████████ ██████

Incorrect. Even if the answer to (C) is "yes," knowing that cars are "sometimes" stolen in daylight hours doesn't give us enough information to determine if there has been some kind of increase that would offset the decrease associated with this program. And (C) doesn't help us determine if it is in fact this program that is causing the decline in thefts.

14%

Will owners who ████ ██████ ██████ ██ █████ ███████ ███████ ███ ███ ████ ██ █████████ ██ █████ ███████ █ ████ ███ █ ████ ██ ████████ ██ ███████

Irrelevant. Whether or not owners who drive cars with these decals will occasionally be "harassed" by police doesn't help us evaluate the claim in the question stem.

Are the neighborhoods ██ █████ ███ ███████ ███ ████ ███ ████ ██████ █ ██████████████ █████ ███████ ██ █████████████ ████ ███████ ██ ███ █████ ██ ███████████ █████ ██ ██████████

Incorrect. Whether or not these neighborhoods are a "representative cross section" of the types of cars owned in all other neighborhoods doesn't actually tell us if this program has caused a decline in car thefts. Even if these neighborhoods aren't representative, a decline in car thefts in these neighborhoods could still be a decline in car thefts overall if there were no relevant increase to offset it, which is a more relevant piece of information. And (E) doesn't help us decide whether it was this program, specifically, that caused the decline.

10%

PrepTest 17 - Section 1 - Question 23

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