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I just took GMATPREP-2 and it was awfully similar to the [#permalink]
04 Dec 2005, 08:03

I just took GMATPREP-2 and it was awfully similar to the actual GMAT that I took 2 mo. ago. I have heard people say GMATPREP is harder but just so you know quants seem to have gotten harder.

Anyways, I got a standard deviation Q in GMATPREP. Unfortunately, I ended up deleting my answers by mistake so I can't paste the exact Q, but..

There was this one Q on which set of numbers have highest standard dev.
Each of the choices have a set of 5 numbers.
I guessed it by picking the set w/ greatest range and lucked out but I don't know how one can answer these questions w/o actually calculating the sd which would be cumbersome and will take > 2 min.

Re: questions on standard deviation [#permalink]
04 Dec 2005, 08:15

try to post the exact question or make the question by yourself.

it not alays true that the greatest sd is one with highest range since sd is depends upon number of observation too. for example.

set A: 1, 2, 3, 4 ,5 ,6 ,7 ,8 ,9
set A: 1, and 8

considering range, the data set 1 should have greter SD because its range is 8 where as the range of the data set is 7. but thats not true and actually the data set 2 has greater sd because the dada set has greater number of observations.

but if all the data sets have equal number of observations, then rang can be used to estimate the gretest SD.

with question, would be easier to discuss in more detail..

But yeah, all data sets have equal number of numbers (5), I think I mentioned that. I don't think ETS expects us to calculate the SD in each case because it is unreasonable for any one to do it in < 2 min.