Of all Critical Reasoning Question Types on the GMAT® , the Inference question is probably the easiest one after the Conclusion Type.

The easiest inference questions are like Chemistry experiments, if green fumes come out it must contain ammonia (or whatever is green). Let us look at the question below:

A company’s two divisions performed with remarkable consistency over the past three years: in each of those years, the pharmaceuticals division has accounted for roughly 20 percent of dollar sales and 40 percent of profits, and the chemicals division for the balance.

Which of the following can properly be inferred regarding the past three years from the statement above?

(A) Total dollar sales for each of the company’s divisions have remained roughly constant.
(B) The pharmaceuticals division has faced stiffer competition in its markets than has the chemicals division.
(C) The chemicals division has realized lower profits per dollar of sales than has the pharmaceuticals division.
(D) The product mix offered by each of the company’s divisions has remained unchanged.
(E) Highly profitable products accounted for a higher percentage of the chemicals division’s sales than of those of the pharmaceuticals division.

One GMAT® Tip that is relevant to all question types is that questions involving stats or numbers have answers that involve an interpretation of the stats or numbers discussed.

In this question, the answer is option C. If the sales of the company is S and the profit P, then the Pharma division has a profit per dollar sales of .4P/.2S=2P/S and the Chemical division has .6P/.8S = 3P/4; hence the latter had a lower profit per dollar of sales.

If you are familiar with the GMAT®, inference questions are also framed in the following ways:

• If the above statements are true, which of the following must also be true?
• Which if the following statements is supported by the argument above?

So in effect, Inference and Assumption questions follow the same logic, if the conclusion is true which of the following must be true!

So, the same negation rule, discussed in this Assumption Question post, has to be used for tougher level inference questions: if the option is not true, will the information in the passage still be valid or true?

Let’s us take the one of the toughest inference questions I have encountered so far and apply the rule.

According to psychoanalytic theory, people have unconscious beliefs that are kept from becoming conscious by a psychological mechanism termed “repression.” Researchers investigating the nature of this mechanism observed occasions on which a patient undergoing therapy became aware of and expressed a previously unconscious belief. They found that such occasions were marked by an unusual decrease in the patient’s level of anxiety.

If the information above is true, and if the researchers’ investigation was properly conducted, then which of the following must also be true?

(A) Changes in the patient’s anxiety level during therapy can generally be used as an accurate measure of the extent to which the patient is becoming conscious of previously repressed beliefs.
(B) Even when one of a patient’s unconscious beliefs remains unconscious, researchers are sometimes able to discover this belief.
(C) If psychoanalytic theory is correct, then most conscious beliefs originate as unconscious beliefs.
(D) Researchers were able to distinguish expressed beliefs that had previously been unconscious from those that had long been conscious but that the patient had not previously expressed.
(E) Although the beliefs on which the mechanism of repression works are all unconscious, the operation of the mechanism itself is something of which patients are consciously aware.

According to the passage, All expression of unconscious beliefs (X) is marked by an unusual decrease in anxiety levels (Y), in terms of pure formal logic All X is Y.

Option (A) is incorrect since it infers All Y is X; All X is Y does not mean that All Y is X. In this case, reduced anxiety need not mean expression of unconscious beliefs, it just be due to expression of conscious beliefs (in other words letting out one’s frustration with the psychiatrist)

The correct option (D) states that when a patient expresses something, researchers are able to distinguish whether it is

• a conscious belief, something he/she was always aware of but only revealed it now or
• an unconscious belief, something that he/she was never aware and only revealed it now.

If this is not true and researchers are unable to make this distinction, then the whole research would not hold since researchers would not be able to label or categorize beliefs as conscious and unconscious in the first place. If that is not possible then the whole study and hence the argument as well falls flat.

The most important thing to remember about GMAT® Inference questions is that they DO NOT require you to draw out possible scenarios based on the information; they are asking you to making logical deductions that MUST BE TRUE if the information above is true. If test-takers evaluate options keeping this in mind, it is impossible to answer an Inference question on the GMAT® incorrectly.

As always feel free to post your queries!