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Confusing necessity with sufficiency on GMAT Critical Reasoning



Confusing necessity with sufficiency on GMAT Critical Reasoning

Confusing Necessity with Sufficiency on CR


In GMAT critical reasoning, there are several different types of questions that you will encounter. In this short article, we will cover the characteristics of questions wherein the trap involves confusing necessary conditions for sufficient conditions.

Confusion between necessity and sufficiency


This error is said to occur when an argument confuses a “necessary” condition with a “sufficient” condition; in other words, this fallacy is the result of assuming that because a condition is needed for a particular outcome, the condition is all that is needed for the outcome.

Please take a look at the following example to better understand this concept.

Example 1: Statement: All humans need oxygen to survive.
Inference: Oxygen is all that humans need to survive.

Here, “oxygen” has been given as a necessity for human survival. However, we cannot, on the basis of this information, state that oxygen is the only thing needed for human survival. Thus, oxygen is a necessity but not a sufficiency, meaning drawing such a conclusion would be confusing necessity with sufficiency. This statement is thus, of course, incorrect.

Now, let’s take a look at a more GMAT-like example. Please try to solve the question before reading further.

Example 2: An independent political campaign can only succeed if it can maintain unity among its political allies and draw voters away from established parties. In the case of Maxwell County, any independent campaign must make a strong statement supporting a higher minimum wage to win over voters, but doing so will likely cause divisions among its political allies.

The claims above, if true, most strongly support which of the following conclusions?

Here, we have a passage followed by a question stem.

Step 1 – Read the question stem.
Step 2 – Read the argument.
Step 3 – Come up with a broad expectation from the correct answer choice.

Take a look at the following answer choice.

Option 1: So long as the independent campaign’s political allies remain in unity, it is likely that the campaign will succeed.

This answer choice is incorrect, it presumes a necessary condition (the campaign’s political allies remaining in unity) to be a sufficient condition, confusing necessity with sufficiency.

Take a look at one more answer choice.

Option 2: Any independent campaign in Maxwell County is likely to lose in the end.

This inference can be correctly drawn, meaning this answer choice is correct.

However, the main point of this article is better exemplified in Option 1, confusion between necessity and sufficiency.

This article has deliberately been kept brief; for a more elaborate explanation, please refer to the Experts’ Global Stage One Critical Reasoning videos.

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