PrepTest 130

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Smoking is correlated with heart disease
Smoking is correlated with drinking caffeine
Therefore - Drinking caffeine is correlated with heart disease

Answer Anticipation:
This stimulus throws a lot of correlation at you ("more likely", "more likely", "positive correlation"). Usually, this would lead to a correlation/causation flaw, but the conclusion here is also a correlation.

Instead, there must be something else wrong with this stimulus, and the flaw here highlights a less common element of correlations that strongly overlaps with quantifiers.

To highlight this, let's say that the correlations in the premises are strong correlations—that most smokers develop heart disease, and most smokers drink caffeine. What inference can we draw from that? Only that some people with heart disease drink coffee. In other words, we couldn't say anything about a tendency for the two to be connected, or a correlation between the two. It's possible that the overlap between those with heart disease and those who drink caffeine ("some" people, i.e., some smokers) could represent .00001% of the population—hardly a correlation.

In short, correlations don't go in both directions, and thus it's hard to draw inferences by combining them.

So here, while smokers might be more likely to develop heart disease, that doesn't mean those with heart disease are more likely to be smokers. Ditto caffeine drinkers and smokers.

How is the correct answer going to highlight this flaw? It's hard to say exactly, but the stem gives us a hint. It asks us to identify a possibility that the argument fails to take into account. Since the argument concludes that caffeine and heart disease are correlated, any answer that brings up the two of those things not going together will serve to point out a possibility this argument doesn't consider.

Answer Explanation:
This answer brings up a comparison between two groups—smokers who drink caffeine, and smokers who don't. The former group is less likely to develop heart disease than the latter. So in the group of smokers, caffeine and heart disease are negatively correlated, not positively correlated as the stimulus concludes, so this answer highlights a possibility that the argument doesn't consider. This answer is therefore correct.

This answer brings up a comparison between two groups—smokers who drink caffeine, and smokers who don't. The former group is less likely to develop heart disease than the latter. So in the group of smokers, caffeine and heart disease are negatively correlated, not positively correlated as the stimulus concludes, so this answer highlights a possibility that the argument doesn't consider. This answer is therefore correct.

Incorrect. First, the argument is over a correlation between heart disease and other factors, not causality, so this answer is a bit out of scope in bringing up a causal factor. Second, there being "more important" factors wouldn't invalidate anything else being a factor.

Incorrect. The conclusion is that drinking caffeine and heart disease are positively correlated, and this answer states that not only are they positively correlated, but it's stronger than another positive correlation. That's not something the argument fails to consider—that's something that would absolutely support the argument.

Incorrect. While limited, a positive correlation is established by this answer, which aligns with the argument and thus doesn't serve as a possibility the argument fails to consider.

Incorrect. If there's a common cause of heart disease and drinking caffeine, then those two things would be expected to be correlated, as an increase in the shared cause would also increase each of the two phenomena, thus creating that positive correlation.