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June 2008 LSAT Section 2 Question 19

The coach of the Eagles used a computer analysis to determine the best combinations of players for games. The analysi...

shafieiava on January 23, 2020

Answer choice A

Why is answer choice A wrong? Is it because of the part of the answer choice that reads opposite of that result. What would be really helpful here is to see an example where if you were to make this answer choice apply to the stimulus how would the stimulus have to be revised?

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SamA on January 24, 2020

Hello @shafieiava,

With information from previous games, the coach has identified a connection between losses and Jennifer's absence. However, this is not enough information to claim that Jennifer guarantees a victory when she plays. Just because the coach has identified a trend, there is no guarantee that this trend will continue in the future. Answer choice D describes this flaw perfectly.

Let's discuss A.
Based on previous games only, what are the sufficient and necessary conditions?
If Jennifer played (JP), then the team won or tied (not L). (Don't get distracted by the tie, I'm just covering all bases in case this is soccer. It's the same as saying not L.)

JP - - - - - - -> not L

In the past, Jennifer playing was sufficient for a win/tie. What is the opposite result, as mentioned in answer choice A? Losing. That becomes sufficient. What is the absence of that previously sufficient factor? Jennifer not playing. That becomes necessary.

L - - - - - > not JP

There is nothing wrong with this! A simply describes the process of making a contrapositive. If the coach were only discussing past game results, this would be valid. The contrapositive is correct, but it is restricted to the past. This is why the coach's error is the attempt to predict the future.

I'll use a simpler example to demonstrate why A is not a flaw in reasoning.

X - - - - - > Y

Opposite Result: not Y
Absence of sufficient factor: not X

not Y - - - - -> not X