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This Logical Reasoning question is from the June 1999 LSAT. It's a good illustration of the “Negation Technique” for assumption questions.
Because the Question Stem is asking for a necessary assumption (an assumption upon which the argument depends), we’re looking for an answer choice that is necessary for the conclusion to logically follow.
Breakdown of the stimulus:
Premise 1: 9 scheduled flights were canceled.
Premise 2: Usually, cancellations are caused by mechanical problems.
Premise 3: It is unlikely there would be mechanical problems with more than one or
two airplanes on a single day.
Conclusion: Therefore, some of the 9 cancellations were probably caused by
something else.
What is the gap between the Premises and the Conclusion? The argument assumes that mechanical problems with 1 or 2 airplanes would not be enough (sufficient) to cause 9 flight cancellations.
However, this ignores the possibility that Swift Airlines may in fact have only 1 or 2 airplanes altogether, with each plane flying 4-5 times a day, so the correct answer is Choice A.
The argument assumes that more than one or two airplanes were scheduled for the nine canceled flights. If this were not the case, the argument wouldn’t work.
If there were only 1 or 2 planes scheduled for all 9 flights, then mechanical problems alone may have caused all the cancellations. The argument depends on this, so it must be true for the Conclusion to follow from the Premises.
Negation Technique: take the opposite of each answer choice. The opposite of any necessary assumption will always make the argument fall apart because that assumption is necessary for the argument to work.
The opposite of Choice A would be “Only one or two airplanes were scheduled for the nine cancelled flights.” If this were true, the Conclusion wouldn’t follow from the Premises, because all cancellations could be due to mechanical problems. The negation of Choice A destroys the argument, and verifying that Choice A is indeed the Necessary Assumption.
Just got my score from the June 2006 LSAT. While I didn't shoot the moon, I did score in the 94th percentile!
ReplyDeleteThank you LSAT Blog. Keep on rocking!
Congrats.You mean June 2005. How much was your score on 180?
ReplyDeleteYes, it was indeed the June 2005 test. A score of 166 landed me in the 94th percentile.
ReplyDeleteCool. I'm taking the Oct 2005 exam. I hope to hit atleast 170. I dont know if I can do it. On the recent official practise tests my average is 165.
ReplyDeleteI was hitting a consistant 163-165 one the various practice tests I took. Best thing to do is to practice under exam-like conditions. 100+ simultanious pencils/coughs/hiccups can be unnerving if you're used to total silence. I recommend praciting at a public library.
ReplyDeleteAlso, the construction going on in the next room during the 4th section of the test was an interesting curveball...
What was your strategy for the Logic Games section? Did you miss out any questions in any of the sections?
ReplyDeleteI haven't gotten my exam back yet, just a raw score and percentile (thank you LSAC-email).
ReplyDeleteas for strategy: do your scratch work (diagrams/charts/whatnot) on the test booklet when you practice. Much as I love the LSAT Blog (which rocks!), I got spoiled by working only one question at a time.
When you've got a five question game section, you can very *VERY* quickly fill up your test booklet with diagrams. Make sure you practice being economical with space on the page as scratch paper is not allowed for this portion of the test.
to repeat: Practice doing all of your diagrams on the test booklet page.
Keep on rocking, LSAT Blog!
I agree with Jeremy that you should mimi test conditions as precisely as possible when practicing. This means taking practice exams in public places near the end, including the actual test center if possible.
ReplyDeleteAlso, be sure to diagram in the books, as noted, and TO USE THE ACTUAL BUBBLE SHEETS! I've had several students who messed up their bubble sheets because they weren't used to them, and this can obviously seriously affect your score, even if you technically understood every question.
Personally, I recommend that you start out taking practice exams in a comfortable, relaxed setting, untimed, using as much scratch paper as you want for diagrams, and just noting the correct answer in your book. However, as you become more comfortable with the exam, begin introducting these other elements (including mock experimental sections), and make sure you do at least a few under actual formal test conditions (5 sections, bubble sheets, fully timed, etc.)