Thursday, July 23, 2009

Logical Reasoning Task Standard: Fix by Adding

Today we'll explain one of the most prevalent of the 23 logical reasoning LSAT task standards: criticizing arguments for overlooking or omitting evidence, which we also call simply, fix by adding.

Not only is this a tricky task standard to identify, it is also often incorrectly lumped into the “consider outside information” ban that causes the issues with scope for many LSAT self-studiers.

Together with fix by removing, this overall task of criticizing arguments accounts for an average of 8 points on a modern LSAT.  LSAC values this task standard as a valuable predictor of performance in law school, as the skills required to criticize evidence use are utilized extensively in analyzing real-world arguments, especially while attacking viewpoints that have otherwise sound reasoning. 

Here are four explanations for how to identify and complete this tricky task, taken from the June 2007 and October 1996 free Sample PrepTests.

In these questions, the LSAT asks you to analyze whether or not the lack of evidence is so obvious an omission by the author as to be a flaw. Criticizing an argument for overlooked evidence can be a tricky task because it requires the test taker to recognize which pieces of evidence are intrinsic to the argument and therefore, by definition, that evidence’s exclusion from the argument is an oversight. It requires the test taker to "fix" the argument by identifying which evidence should be addressed and/or countered.

This is in contrast to the “weaken with external evidence” task standard, which introduces new evidence—which could not have been expected to be known—that casts doubt on the argument’s conclusion after it has already been made.

Yet another task standard that is easily conflated with criticizing evidence use is “finding the error in logical strategy”--fix by removing--which covers such common mistakes as ratios to rates, inferring causality from correlation, and improper argument strategies or reliance on principles. Again, outside evidence should not be considered for this task standard, as the error is within the stimulus.

Now you can see why LSAT tutors and self-studiers alike become frustrated when trying to determine when to incorporate outside evidence while answering logical reasoning questions.

In order to correctly answer this task, the test-taker must switch strategies within the same question to evaluate each answer choice. This is why our Zen students practice changing scope within the same question and why it is difficult to say: “Do not ever consider outside information for this question stem.”


Above is a gallery of the logical reasoning sections that have a greater than average density of the task, and below is the frequency that this task has been asked on modern LSATs and the percentage change in frequency from pre-2007 LSATs. It averages 7.7% of the points on a modern LSAT, and you can reasonably expect at least two points to be devoted to identifying overlooked evidence.
    35 times
    on LSATs since 2007
    7.7% of LR
    (4 per LSAT, range 2-5)
    0.1% growth from pre-2007