Critical Reasoning Assumptions: The Denial Test
What is the purpose?
Any test-taker in possession of at least some experience with GMAT's Critical Reasoning problems is familiar with the situation when two or more answers seem equally plausible. Having eliminated a couple of choices with relative ease, you still find yourself hesitating to choose among the remaining options. Although there is no technique to double-check your answers for all CR question types, there is such a technique for Assumption questions. It is known as the denial test, and it is a perfect tool for deciding among equally attractive answers or for confirming that the choice you have made is the right one.
How do I do it?
The denial test includes two simple steps.
The first step is to come up with the opposite of a statement given in the answer choice, a negation. Be very careful here— logical negation is a little different from what your real life experience could prompt you to do. We will examine proper negation on GMAT later.
The second step is to check whether your "opposite" statement, your negation, weakens the conclusion. If the conclusion no longer works, the assumption in the answer choice is relevant, i.e. it matters to the validity of the argument. If, conversely, the conclusion still seems well grounded even when the assumption denied, then this is not an essential assumpton for connecting the premises with the conclusion and is therefore not necessarily assumed in the argument.
To see how the denial test works, look at the example below:
The latest literacy development program in Country X has clearly been a success. Ten years after its start, only 5% of citizens in Country X are illiterate.
On which of the following assumptions does the argument rely?
A) The literacy rate in Country X was not the same when the program started as when it ended.
B) All illiterate citizens took part in the program.
The premise of this argument is that only 5% of citizens are now illiterate. The author cites this figure as the basis for his conclusion that the literacy development program was a success and that now there are fewer illiterate citizens than before the program was introduced. Since the argument does not explicitly include the lower literacy rate prior to the beginning of the program, this information must be assumed if the conclusion is to be sound.
Look at Choice B now, a tempting answer choice: if all citizens participated, then the program must have been successful. However, if you deny this statement, you will get "NOT ALL illiterate citizens took part in the program." Does this statement in any way undermine the conclusion? It does not, because it's enough know that at least some illiterate citizens participated, apparently learning to read and write and thus reducing the illiteracy rate. The program, therefore, could very well be successful even if not all illiterate citizens took part in it.
If you negate Choice A, however, you will get "The rate of literacy was THE SAME before the start of the program." It means that no increase in the literacy rate had occurred by the end of the program. Since this directly contradicts the conclusion, the denial test confirms that for the conclusion to be valid, it is necessary to assume that the rate of literacy was NOT the same at the beginning of the program.
How do I deny correctly?
As you have just seen, it does not take much to deny a statement on GMAT. As a rule, adding NOT to a sentence, or removing it if it is already there, will suffice. The most important thing to keep in mind is that your goal is to come up with a statement that denies the truth of the answer choice in the least extreme way.
For example, if asked what is the opposite of white, most people will say black. However, in terms of logic, the opposite of white is everything that is NOT white. The same rule applies to concepts such as always. Although your common sense might prompt you to use never as the opposite of always, on GMAT you need to use the least extreme opposite, namely NOT always. So when you need to negate a statement like, "I always wake up early," you shouldn't go to such extremes as, "I never wake up early" or "I always wake up late." Saying "I DO NOT always wake up early" is enough because it successfully denies the statement.
In addition to always, several other qualifiers often appear in typical assumptions on GMAT. The instructions below will guide you in properly denying statements containing these other words.
All/ NOT all:
All left-handed people are creative.
Opposite: NOT all left-handed people are creative.
Some left-handed people are creative.
Opposite: NO left-handed people are creative.
Left-handed people sometimes demonstrate exceptional creativity.
Opposite: Left-handed people NEVER demonstrate exceptional creativity.
If you are not sure how to negate a particular assumption, you most likely can accomplish it by using the words NOT NECESSARILY. Thus, you will get a statement that denies the truth of the original assumption in a way that is not too extreme.
In deciding to rely on the denial test, keep the following key points in mind:
• Use negation to decide between two equally tempting choices or to confirm that an answer choice is correct.
• Don't attempt to deny every single assumption—it will be too time-consuming, and there are usually faster ways to eliminate the choices that are most obviously wrong.
• Deny the statements in question in the least extreme way—proper negation is crucial to successfully determining the relevance of an assumption.
- GMAT Critical Reasoning: How to Strengthen an Argument
- GMAT Critical Reasoning: Weakening Question
- How to Approach GMAT Critical Reasoning Questions