Math question for PCAT!

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217933

Does anyone know how to do this problem and explain how to do it? 🙂

What is the variance of the data: 1,2,3,4,5,6,7,12?

Choices are:
A. 84
B. 2/21
C. 8
D. 21/2

Thanks! 😀
 
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from yahoo answers:

To find the variance, subtract the mean from each number in the set, square the result, and then take the sum. That is, if X represents a number in a set and u represents the mean value of that set, the variance is the Σ(X - u)^2.
 
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It looks like you can do it without doing much math. To find variance, you don't divide so it isn't B or D. You do have to find the mean which you can figure out roughly by looking at the numbers. It looks like it is about five or six. Then you have to subtract the mean from each number and square it. But if you assume the mean is 5 (it really is) then 12-5=7. Square that and you have 49 already and you haven't even done the whole problem. Clearly it isn't C. No need to waste any more time finding the true answer of A. If you do solve it out by hand, it will chew up your time that would be better spent on other problems.
 
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To the OP: Where did you get this question? For some reason, I don't see them asking something like this....I could be wrong though.

PS- Good reasoning diastole
 
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diastole said:
It looks like you can do it without doing much math. To find variance, you don't divide so it isn't B or D. You do have to find the mean which you can figure out roughly by looking at the numbers. It looks like it is about five or six. Then you have to subtract the mean from each number and square it. But if you assume the mean is 5 (it really is) then 12-5=7. Square that and you have 49 already and you haven't even done the whole problem. Clearly it isn't C. No need to waste any more time finding the true answer of A. If you do solve it out by hand, it will chew up your time that would be better spent on other problems.
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I don't know what you're talking about but the answer is D, 21/2 or 10.5
 
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The Kaplan book is actually more difficult than the actual pcat in my opinion... but if you do get a question like this... don't waste time... just fill in with a random answer.
 
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There will be some statistics stuff like that on the PCAT.

I know I've seen a few questions asking about the distribution curve and to know how to solve it you'd have needed the 68-95-99.7 (forgot the exact percentages) rule, which determines the number of standard deviations from the mean. Not exactly a stats buff but something like that, lol. I somehow managed to forget that basic rule on the PCAT even though I've only done stats about, oh, 8 months ago.
 
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