Sunday, September 28, 2008
I took the "Sample LSAT Critical Reasoning Section" to bed with me last night. There were 25 problems, and you're supposed to do them in 35 minutes. I took 31 minutes, and got 2 wrong. Note that it was 3 am, and I wasn't what you'd call sharp or motivated, and I know what I missed on one of them.
The other, however, I have a major beef with. Their answer is WRONG! It's the conventional answer, but it's wrong.
This is the problem (it's #9 here):
9. Mrs. Mason is gifted with psychic powers that enable her to foretell future events. In the past, Mrs. Mason has predicted such actual events as the election of President Clinton, the stock market crash of 1987, and the St. Loius Cardinals' 1982 World Series victory. These are just a few of Mrs. Mason's accurate predictions. The answer to which of the following questions would be most useful in evaluating the strength of the argument above?
A) What percentage of Mrs. Mason's predictions has come true?
B) Could the election of President Reagan have been predicted without the help of psychic powers?
C) What is the actual mechanism by which Mrs. Mason's psychic powers are supposed to operate?
D) How long before the events in question did Mrs. Mason make her actual predictions?
E) Do most scientists accept the idea that the power to predict the future through psychic means really exists?
Note that "useful in evaluating the strength of the argument" does not mean it helps to make the statement sound truer. It means that it most helps you to decide the validity or invalidity of the statement. Subtle difference there. Another way to think of it, if you could ask one question and one question only to decide whether to believe the statement or not, what would that question be?
"B" can be thrown out immediately as having no relevance (although if it had said "Clinton", it might have a lot. Perhaps it was there to catch the unwary). "C" can be discarded because knowing whether she uses a crystal ball or a spirit guide doesn't matter. "E" I'd throw out because any answer wouldn't have a bearing on this particular case. That left "A" and "D".
If I ask "A", and get "90% of her predictions are accurate", that sounds good, but it still leaves me with questions concerning the validity of her predictions. If I get "10%" of her predictions are accurate, it doesn't make a lot of difference to me. 90% of easy predictions is not 9 times better than 10% of difficult predictions, and there is no indication of the difficulty of her predictions. So knowing that number is not helpful. It does NOT make it easier for me to evaluate the strength of the argument.
Let's try "D". If the answer is "She has made all of these accurate predictions at least 2 years before the events in question", then hey, now we've got something to go on. That's a strong point. Or it could be "She made these accurate predictions three minutes or fewer before the actual results were announced." Whoa! Blows the argument out of the water. Any idiot can do that. Either way, whatever the answer, I DO have more useful information to evaluate the strength of the argument.
So, I answered "D".
They wanted "A".
I don't agree.
"A" is the conventional answer. Their argument is: "The passage cites just three accurate predictions by Mrs. Mason and alludes to others. However, the existence of three successful predictions means nothing by itself; one would need to know what percentage of Mrs. Mason's predictions has been accurate (or inaccurate). A success rate of 95 percent would mean that she is almost surely a legitimate talent [Me - not if all of them were made moments before the event!]; a success rate of 5 percent would strongly suggest that she is a fraud.
Ok. Who do I write to....
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