Let’s take a close look at three actual LSAT logical reasoning questions from LSAC PrepTest 19. Try each question on your own, and then check out the explanations from Kaplan’s test experts and see if your thought process matched ours. The questions are copyrighted property of the LSAC. Without further ado:
Question 1 Answer and Explanation
By checking the stem first, you know to look out for a logical flaw from the get-go, and perhaps you spotted it in the shift from “probably” in the evidence to “definitely” in the conclusion. Sara probably has the same illness as Michael, and he definitely doesn’t have a strep infection. Therefore, the author concludes, Sara definitely doesn’t have one either. Uh-uh. The most we can conclude from this evidence is that Sara probably doesn’t have a strep infection. As (D) points out, evidence supporting a probable conclusion is erroneously being used to support a definite one.
Question 2 Answer and Explanation
The author argues that the implementation of a flextime schedule will increase production, because flextime increases morale. Period, end of story. Kind of leaves us hanging, doesn’t it? The author leaves us to our own devices to fill in the most important part of the argument, namely, a connection between increased morale and increased production. This connection, stated in (B), must be assumed by the author if the conclusion in the first sentence is to remain valid.