Succeed on Critical Reasoning GMAT Questions with This Causation Tip

causation goslingOh, causation on the GMAT.  Why do you cause so much stress in people’s lives?

Success on many Critical Reasoning questions really comes down to understanding whether one thing (“X”) causes another thing (“Y”) or not. For example, I moved to New York in 2007. Shortly thereafter, there was a huge drop in the New York stock market. Did I cause the crash (Y) simply by moving to New York (X)?

Of course I did! But that’s beside the point.

Take a look at the following question from an MBA.com practice CAT:

The growing popularity of computer-based activities was widely predicted to result in a corresponding decline in television viewing. Recent studies have found that, in the United States, people who own computers watch, on average, significantly less television than people who do not own computers. In itself, however, this finding does very little to show that computer use tends to reduce television viewing time, since_______.

Which of the following most logically completes the argument?

Let’s not even look at the answer choices yet. We can do quite a bit of “pre-work” on a question like this before the answer choices begin to sway us in various directions.

In the simplest terms, the argument states that some believe:

An Increase in Computer Usage (ICU) causes a Decrease in Television Watching (DTW).

And this makes some logical sense, right? We only have a certain number hours per day, and if we spend some time on our laptops, we might not have as much time to catch up on Girls and Shark Tank.

The argument then goes on to state a bit of evidence that seems to support the initial prediction:

Computer Owning (not quite the same as ICU, but in the same ballpark) actually correlates with Watching Less Television (DTW).

However, the argument then, a bit paradoxically, states that even though “Computer Owning and DTW” seem to happen at the same time, it is not the case that “ICU causes DTW.” Interesting.

Well, whenever you see a case like this on the GMAT, you’re better off coming up with a possible answer or two before checking out the answer choices. When the GMAT says that “X and Y happen together, but X did not cause Y,” a very strong possibility is that “Z” actually caused Y. What is Z? Z is anything else that might have caused Y.

Here are some possible answer choices that would work:

  • People can generally only afford either one computer or one television (implying that ICU doesn’t cause the DTW, but the price of a computer might).
  • Computer owners tend to be overworked professionals who have very little leisure time (implying that ICU doesn’t cause DTW, but a pre-existing condition of computer owners is strongly correlated with DTW before the computer usage is even mentioned).
  • Computers create an electromagnetic field that disables televisions from turning on (implying that ICU doesn’t cause DTW, but the physical properties of owning a computer might).
  • Computer owners, at the point of purchase, were forced by the Illuminati to sign a document swearing never to watch television under the penalty of jail time (implying that ICU doesn’t cause DTW, but intense pressure from an underground fraternity might).

At this point, you might be saying, “Whoa, those answers were totally out of left-field.” Indeed, you’re right. When the argument concerns X’s and Y’s, and we’re looking for a Z (something else that might have caused Y), then the correct answer might very well be out of left-field. Do not eliminate an answer simply because it seems random or unexpected. Instead, simply focus on the chain of logic. If your out-of-left-field Z supersedes X as the primary cause of Y, you’ve done a great job of weakening the causal link between X and Y.

Now let’s look at the real answer choices:

(A) many people who watch little or no television do not own a computer.

(B) even though most computer owners in the United States watch significantly less television than the national average, some computer owners watch far more television than the national average.

(C) computer owners in the United States predominately belong to a demographic group that have long been known to spend less time watching television than the population as a whole does.

(D) many computer owners in the United States have enough leisure time that spending significant amounts of time on the computer still leaves ample time for watching television.

(E) many people use their computers primarily for tasks such as correspondence that can be done more rapidly on the computer, and doing so leaves more leisure time for watching television.

Boom. Answer choice C basically says that ICU doesn’t necessarily cause DTW, because the demographics of computer users correlate strongly with DTW independently of actually using the computer. While this answer choice does not exactly provide a direct cause of DTW, it does strongly weaken the causal link between ICU and DTW, and that should be your main goal.

Does a “Z” always represent the answer on GMAT causation weakeners? Not always, but it occurs frequently enough that it’s worth spending 5-10 seconds coming up with one or two Z’s on a question like this. If nothing else, doing so can help solidify a more complete understanding of the argument.

Hopefully this Blog Post (BP) will cause you to Do Well on Your GMAT (DWYG). When was the last time BP caused something good to happen?

Are you studying for the GMAT? We have free online GMAT seminars running all the time. And, be sure to find us on Facebook and Google+, and follow us on Twitter!

By David Ingber