LSAT Conditional Reasoning - The Domino Effect

Posted by Adam M. Tyson on

In my previous blog post I talked about the basics of conditional reasoning on the LSAT, and dealt with fairly simple statements involving a single sufficient condition and a single necessary condition. You’ll find that post here:

http://blog.powerscore.com/lsat/lsat-conditional-reasoning-easy-as-falling-off-a-log

On the LSAT, though, things are not always that simple! Sometimes (often, really) you will encounter conditional chains, where one thing is sufficient for another, which is sufficient for a third, which is sufficient for a fourth. Stringing these conditional claims together in the right order, and then knowing which conditions affect others and in what ways, will be crucial to your success. You will encounter chains in Must Be True questions, Parallel Reasoning, Parallel Flaw, Justify the Conclusion, and others. So, how do you manage to interpret the relationships correctly?

By playing with dominoes!

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Topics: LSAT Logical Reasoning, LSAT Prep, LSAT Conditional Reasoning

LSAT Conditional Reasoning - Easy as Falling Off a Log

Posted by Adam M. Tyson on

Conditional reasoning – argumentation based on “if…then” statements – is a prominent feature of the LSAT. While the numbers vary from test to test and year to year, you can expect something in the neighborhood of 10 questions in the Logical Reasoning sections that involve conditional reasoning, and at least half of the Logic Games will employ it as well. Some games (typically undefined or partially defined grouping games) will be entirely conditional, with every single rule setting up an if…then statement (if R is on the committee, X is also on the committee; if W is not on the committee, S is on the committee; etc.). In short, while conditional reasoning is not the be-all and end-all of the LSAT, it is a subject that should be mastered if you want to do well on the test, and it therefore deserves attention and practice.

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Topics: LSAT Logical Reasoning, LSAT Prep, LSAT Conditional Reasoning

Negating conditional statements on the LSAT

Posted by Nikki Siclunov on

Granted, most Logical Reasoning questions with conditional reasoning won’t require you to negate the conditional relationships in them. You will certainly need to know what the contrapositive is, and—if there are multiple conditional relationships—you need to know how to form a conclusion by combining them into a chain (aka the “law of syllogism”).  Occasionally, in Justify questions, you will need to establish a logical link between the premises and the conclusion. And in Flaw questions, you will need to know how to describe in abstract terms the most common logical fallacies involving conditional reasoning.

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Topics: LSAT Logical Reasoning, LSAT Prep, LSAT Conditional Reasoning

LSAT Conditional Reasoning: When To Diagram

Posted by Dave Killoran on

A question that frequently comes up from readers of the LSAT Logical Reasoning Bible is, when should I diagram conditional statements in the LSAT Logical Reasoning section? In the book, I talk about diagramming in a number of different chapters, but most prominently in the chapter on Conditional Reasoning.

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Topics: LSAT Prep, LSAT Conditional Reasoning

How to Avoid the Two Most Common Mistakes in LSAT Conditional Reasoning

Posted by Jon Denning on

A student of ours who's working through the PowerScore Logical Reasoning Bible asked a common question the other day, and I want to share it, and my response, with you.

Specifically she's been struggling with Mistaken Negations and Mistaken Reversals in conditional reasoning, and asked if I could help her better understand those two errors.

Here's my reply:

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Topics: LSAT Logical Reasoning, LSAT Prep, LSAT Conditional Reasoning

The Most Dangerous Conditional Rule on the LSAT

Posted by Dave Killoran on

On our LSAT Discussion Forum recently, I've been running into a recurrent question about conditional reasoning. these questions revolve around a really tricky point, and one that has devastated test takers when it has appeared on previous LSATs. But if you can learn the idea, it takes something the test makers expect to be very difficult and turns it into something fairly easy. Plus, it's not that tough to learn. So what is this mysterious but critically important concept?

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Topics: LSAT Conditional Reasoning

Negating Compound and Conditional Statements

Posted by Nikki Siclunov on

The ability to logically negate a statement—whether conditional, causal, etc.—is critical to your success on the LSAT. It comes up most commonly in the Logical Reasoning section of the test, although any question stem using the word “EXCEPT” (always capitalized) will require you to logically negate that stem. The list does not stop here: every time you apply the contrapositive of a conditional statement, you will need to reverse and negate the two conditions that constitute that statement (this is relevant to Must Be True, Justify, and Parallel Reasoning questions mostly, but can also be critical in other sections of the test). Negating statements is also useful in Assumption questions, because proving the correct answer choice requires application of the Assumption Negation Technique: the correct answer choice, when logically negated, must weaken the conclusion of the argument. And, of course, the ability to understand the logical opposite of a conditional statement will be directly relevant to many Cannot Be True questions, where the correct answer choice is the one that can be disproven using the information contained in the stimulus. 

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Topics: LSAT Prep, LSAT Conditional Reasoning

LSAT Conditional Reasoning Practice: Test Your Skills

Posted by Jon Denning on

The other day I came across an apparently famous logic puzzle called The Wason Selection Task. I say "apparently" famous because I for one had never heard of it, but I was instantly struck by the conditional nature of the process in question.

If you're reading this I presume you've got some experience with LSAT conditionalityand if you'd like more I've included a number of helpful links at the end of this post!so let's put your knowledge to the test.

Take a look at the picture up top, where four cards are arranged before you, two with numbers, and two with colors. What you're told of these four cards is that each of them has a positive, whole number on one side (two of which are exposed at the moment) and a color on the other (again, two of which are shown). So the 3 and the 8 have a colored back, and the red and the orange have a numbered back. Simple enough right?

Here's the question then. Of those four cards, which card(s) MUST be turned over to test the rule that "if a card has an even number on one side, then its other side is red"? Indicate only the card(s) needed (that is, with the potential) to determine whether that rule has been broken here.

Think you've got it? 

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Topics: LSAT Logic Games, LSAT Logical Reasoning, LSAT Conditional Reasoning

Should I Study Formal Logic in College to Prep for the LSAT?

Posted by Nikki Siclunov on

Given the emphasis on Logical Reasoning on the LSAT, students often wonder if they are missing out by not taking formal (or deductive) logic in college. Granted, some exposure to deductive logic doesn't hurt: at their best, such courses will teach you the fundamental concepts of symbolic logic, help you understand the difference between valid and invalid arguments, and train you to use symbolic language to display the logical structure of complex arguments and statements. You will probably learn to analyze truth-functions ("and", "or", "not", "if...then"), as well as quantifiers ("all", "some"), which will ultimately help with conditional reasoning on the LSAT. Indeed, students who were exposed to formal logic before undertaking a test prep course with us seem to derive some benefit from it, judging from their performance in class and on their practice tests. However, think twice before you register for a Logic course at your local college this coming Fall. Here's why:

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Topics: LSAT Logical Reasoning, LSAT Prep, LSAT Conditional Reasoning

LSAT Conditional Reasoning 101: Circular Reasoning and the Contrapositive

Posted by Dave Killoran on

Recently, in our LSAT Forum, a student asked me about the existence of circular reasoning in a question that appeared to use the contrapositive. And, from appearances, the question did use the contrapositive but the reasoning was still flawed, precisely because of the way it was used. Because so many people become used to the contrapositive and eventually take it for granted, questions that trade on the point raised in the question can be very difficult to solve. Let's look at what happened in more detail.

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Topics: LSAT Prep, LSAT Conditional Reasoning