GMAT Tip of the Week: Beware the Coincidence

GMAT Tip of the WeekToday marks the 50th anniversary of the assassination of US President John F. Kennedy, and amidst all of the memorial articles and TV specials and conspiracy theories, you’ll undoubtedly see that email forward that details the eerie similarities between the two presidents assassinated almost 100 years apart, Kennedy and Abraham Lincoln:

– Kennedy had a secretary named Lincoln, and Lincoln had a secretary named Kennedy
– Both men were assassinated by men with three names (Lee Harvey Oswald and John Wilkes Booth), each containing 15 letters
– Both were elected in ’60, and then succeeded by vice presidents named Johnson, etc.

And while it’s fascinating every time you read it, it’s just a bunch of coincidences. Even the flaxseediest protester in front of the White House can’t put together an argument for why any of those coincidences could possibly scream “conspiracy” or anything other than “sometimes there are coincidences.” No matter how much significance we want to ascribe (but Kennedy was killed in a LINCOLN town car, and Lincoln is owned by Ford, and Lincoln was shot at Ford’s Theater!) to events that happen concurrently, often those things are just coincidences. And realizing that “coincidences happen” can help you master Critical Reasoning problems.

Much like the Lincoln-Kennedy coincidences, other coincidences happen frequently on the GMAT and bait us into trying to see them as related. Consider these facts:

Beginning in the early 1990s, New York City instituted a program called “broken window policing,” in which even small acts of vandalism or petty crime were actively pursued, prosecuted, and corrected. The prevailing wisdom was that such policing would both send a message to would-be criminals and encourage all citizens to take more pride in their city and each other. Between 1994 and 2001 the violent crime rate steadily decreased by over 50%, from a rate of 1,861 violent crimes per 100,000 people in 1994 down to 851 violent crimes per 100,000 people in 2001.

What can you conclude? Your mind wants to see the “broken window policing” policy as the cause of that dramatic decrease in crime. But based simply on the above can you prove it? What if the two are just coincidences; what if a massive decrease in the unemployment rate or (as predicted in the bestseller Freakonomics) a dramatic decrease in the birth rate of potential criminals were the drivers? When you’re presented with those facts above, your mind naturally tries to link them together, but in GMAT Critical Reasoning you have to consider the idea that two concurrent facts – no matter how much they might seem related – could just be coincidences. Consider this problem:

About two million years ago, lava dammed up a river in western Asia and caused a small lake to form. The lake existed for about half a million years. Bones of an early human ancestor were recently found in the ancient lakebottom sediments on top of the layer of lava. Therefore, ancestors of modern humans lived in Western Asia between 2 million and 1.5 million years ago.

Which one of the following is an assumption required by the argument?

(A) There were not other lakes in the immediate area before the lava dammed up the river.
(B) The lake contained fish that the human ancestors could have used for food.
(C) The lava under the lake-bottom sediments did not contain any human fossil remains.
(D) The lake was deep enough that a person could drown in it.
(E) The bones were already in the sediments by the time the lake disappeared.

When you read the stimulus here, you’re likely to accept it as pretty airtight truth. The bones in that part of the fossil record are proof that people lived during that time period, right?

But what if the bones are just coincidentally in those sediments? The ONLY evidence we have is those bones, so before we take this conclusion at face value we should consider whether they’re really the smoking gun that they’re set out to be. And there’s the possibility that they just coincidentally happened to be in that part of the sediments during whatever archaeological dig found them. Perhaps they were much more recent but an earthquake shook them down a few hundred thousand years deeper into the sediments; perhaps Lee Harvey Oswald III and his punk teenage friends decided to play a trick on the archaeologists and deposited the bones (of a man named Lincoln?) in that sedimentary zone as a prank. If you can see that “bones in the sediment now” doesn’t necessarily “bones in the sediment during that timeframe” – if you can see that it might be a coincidence – you’ll realize that answer choice E is necessary to take away the coincidence factor.

Notice, too, about this problem that it’s of the “Assumption” variety. Quite often Assumption questions are hard mainly because it’s so easy to buy the argument at face value – to see two concurrent items as causal or related because they just seem so likely to fit. That’s why it’s important to make sure you emphasize the “Critical” part of Critical Reasoning. Do not buy the argument – keep in mind that two events could always be coincidental or correlated if you don’t have definite proof that one caused the other.

Heed this wisdom, and your 700+ score will be no strange coincidence.

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By Brian Galvin