Conditional Statements In Critical Reasoning

by on November 29th, 2012

Today’s post come courtesy of Veritas Prep GMAT instructor, Karishma.

Let’s discuss a very important concept of Critical Reasoning — analyzing a conditional statement. You will often encounter these even though they may not be in the exact same format as the one we will discuss below. We will discuss the basic framework and then we will look at questions where this concept will be very helpful. Mind you, without this framework, it can get a little tricky to wrap your head around these questions.

Statement 1:

If you trouble your teacher, you will be punished.

What does this imply? It implies that ‘troubling your teacher’ is a sufficient condition to get punished. If you trouble, you will get punished.

What about the other way around? What if you got punished? Can we say that you troubled your teacher? No! You could have got punished for something else. Mind you, troubling your teacher is not a necessary condition to get punished. There could be other things that could lead to punishment.

On the same lines, what if you didn’t trouble your teacher? Can we say that you didn’t get punished? Hope it makes sense to you that it is not necessary that you didn’t get punished. You could have been punished for something else.

What if you didn’t get punished? Does that imply something? Sure! We can say that you didn’t trouble your teacher and you didn’t do anything else that could get you punished.

To write it succinctly,

Statement: If A, then B (A is sufficient for B to happen)

A implies B

B does NOT imply A

‘Not A’ does NOT imply ‘Not B’

Not B’ implies ‘Not A’

Notice that you can replace ‘if’ by ‘when’ or ‘whenever’.

Statement 2:

Only if you work hard will you succeed.

What does this imply? It implies that hard work is a necessary condition to succeed. Note here that it may not be sufficient to succeed but it is definitely necessary. Along with hard work, you might need smarts and luck on your side too.

What if you know that Tom worked hard? Can you say he succeeded? No, it is not necessary. As discussed, only hard work may not have been enough. It was essential but it may still not have led to success.

What if you know that Tom succeeded? Can we say that he worked hard? Yes! Since he succeeded and hard work was essential to succeed, he must have worked hard.

Let’s look at it the other way now. What happens when Tom doesn’t work hard? We know that in that case he certainly doesn’t succeed. Hard work is essential to success. No hard work implies no success.

On the same lines, what about the case in which we know that Tom didn’t succeed? Can we say whether he had worked hard or not? No. He may or may not have worked hard. Since there could have been other conditions required to succeed, we don’t know what led to failure.

To write it succinctly,

Statement: Only if A, then B (A is necessary for B to happen)

A does NOT imply B

B implies A

Not A’ implies ‘Not B’

‘Not B’ does NOT imply ‘Not A’

Notice that you can replace “only if” with “only when.”

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