Common LR Answers (LSAT)

Two answer choices you might see on the LR section of the LSAT:

"Confuses a necessary condition for a sufficient condition" 

and

"Confuses a sufficient condition for a necessary condition."

Let's examine both.

"Confuses a necessary condition for a sufficient condition" 

Imagine you were to go the doctor and the doctor told you that only if you cut down on red meat would your cholesterol levels drop. So, you do as told and cut down on red meat. Your cholesterol levels don't drop. You then claim that the doctor's advice was wrong.

It's important to remember that the doctor said that only if you cut down on red meat would the levels drop. What the doctor did not say is that the only thing you need to do for the levels to drop is to cut down on red meat. It's entirely possible even taking the doctor's advice as given that cutting down on red meat alone would not drop the levels. 

We know, if taking the doctor's statement as true, that if you don't cut down on red meat the levels will not drop. We do not know that if you do cut down on red meat the levels will drop. Said otherwise, cutting down on red meat is a necessary condition for the levels dropping, but it's not a sufficient condition for the same. And so by claiming that the doctor's advice was wrong you will have mistaken a necessary condition for a sufficient condition. 

"Confuses a sufficient condition for a necessary condition."

Now, instead of the above, let's assume that the doctor tells you that all you'll need to do to lower your cholesterol levels is to cut down on red meat. You don't do as the doctor says and so you believe that your levels will not drop. 

Here, the doctor did not say that cutting down on red meat was required for the levels to drop; the doctor said that cutting down on red meat would be enough for the levels to drop. In other words, the doctor said that cutting down on red meat was a sufficient condition for the levels dropping but not a necessary condition for the same. And so by believing that the levels will not drop simply because you did not follow the advice, you would be mistaking a sufficient condition for a necessary condition. 

Try to understand this distinction as well as possible. It shows up repeatedly on the exam!