Wednesday, February 24, 2010

Logical Reasoning Zen Task Standard: Fix by Removing

As we mentioned, during February we'll be going through the 22 different Zen task standards on the logical reasoning section of the LSAT. We feel that this LSAT classification system is more comprehensive than other methods of categorizing the section, as it not only breaks down the section by question stem, but how to perform the task to receive credit.

For today we'll explain how we approach one of the tasks, fix by removing, that we think most other test prep companies gloss over. As we mentioned when we introduced fix by adding:

A task standard that is easily conflated with criticizing evidence use is “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.
You can recognize these two tasks by a question stem that has one of the keywords "criticism," "flaw," or "counters," but does not include an "if true" conditional. "If true" indicates that you will be required to evaluate new evidence--commonly to strengthen or weaken the argument--unlike the fix by tasks, which are limited to the topics presented in the stimulus.

Unfortunately, there is no clear-cut method for determining whether you will be fixing the argument by adding evidence or removing an error. Consequently, you should approach any stimulus with a fix by stem as though it has a logical error; if you can find one, you should clearly prephrase what the error is and then look for an "LSAT speak" translation in the answer.

Common errors, in no particular order of incidence, include:

  1. Conflates cause and correlation
  2. Conflates necessary and sufficient
  3. Treats probabilities as absolutes
  4. Inappropriately generalizes evidence or analogies
  5. Incorrectly applies rates/ratios/percentages to hard numbers
  6. Attacks the speaker rather than the argument
  7. States contradictory claims
  8. Utilizes contradictory evidence
  9. Employs ambiguous use of terms
  10. Assumes the conclusion (circular logic)
  11. Parts to whole
  12. Whole to parts
If you can identify any of these errors while reading a stimulus, you will likely be able to turn that prephrase into an easy point by searching for the correct answer. Distractors may, and often do, include new evidence that would weaken the argument, which are inherently irrelevant to the the task of evaluating the argument as it is written: this is commonly called being "out of scope."

Other attractive distractors may be fix by adding answers for a stimulus. If an argument has one of the above errors, the correct answer will always be a restatement of the element that must be removed rather than a fix by adding answer.

We advise our clients to read the stimulus looking for any of the common errors. If they find one, they must clearly pre-phrase a statement that states that error. A Zen student then holds that pre-phrase in their mind while evaluating each answer choice, seeing if the LSAT speak matches their pre-phrase.

The example we chose for this task is taken from the Sample Questions with Explanations document on LSAC's website. The question stem for fix by is the same for both tasks, so you have no choice but to approach them in the same way. You should be actively reading the stimulus and marking it with both highlighter and pencil, focusing on identifying any of the common errors. After an initial reading, you should be able to underline and/or prephrase the error. See if you can identify the parts of the argument we highlighted in different colors as you read through the stimulus below.

Hopefully you identified that the two phrases in yellow highlight are two different and contradictory conclusions. If no one with a sore throat should seek medical attention, how can people with the first symptoms of epiglottitis (a sore throat) seek medical attention?

This is a perfect example of a fix by removing stimulus and answer: no amount of new evidence (i.e. a fix by adding
answer) will rectify the contradiction inherent to the argument. Some element of the argument must be removed in order for it to stand, which is why we decided to name the task fix by removing.

Below are the four distractors, each a restatement of one of the above mentioned common errors. See if you can identify the prephrase that each one matches; hover over the images to see the "correct error."





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 5.6% of the points on a modern LSAT, and you can reasonably expect that at least two points will be devoted to finding common argument errors.

21 times
on LSATs since 2007
5.6% of LR
(~3 per LSAT, range 0-4)
-1.5% growth from pre-2007

The negative growth doesn't necessarily mean that LSAC considers finding common errors less important than it used to, as it has been consistently volatile across modern LSATs. This task is a microcosm of the shift from analyzing argument structure to evaluating evidence use; although the two fix by tasks seem similar on the surface, they are actually utilizing totally different skills. The newest LSATs expect you to automatically analyze the stimulus' structure and then apply that analysis to more complicated tasks. Thus, while finding errors is not as valuable a skill as it used to be, practicing it can help you correctly answer a variety of other tasks in more complicated strands.

According to LSAC:

This test question is a “very easy” item; 91 percent of examinees answered it correctly when it appeared on the LSAT.