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# Std deviation gmat prep

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Intern
Joined: 25 Jul 2006
Posts: 44

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07 Dec 2006, 01:47
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

need some explanation on this guys...do help...i am getting 5 thgh the OA is 2...

Cheers!!
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Director
Joined: 06 Feb 2006
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07 Dec 2006, 02:12
100-22,4=77.6

Only two values are below......

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Manager
Joined: 03 Jul 2005
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Location: City

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07 Dec 2006, 05:42
Also 2 for me.

I nearly got caught out, did you get 5 by including what is above as well!

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Manager
Joined: 25 Nov 2006
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07 Dec 2006, 11:56
Could anyone help me out in finding a link which could brush my basic on Standard Deviation.

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Senior Manager
Joined: 20 Feb 2006
Posts: 373

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07 Dec 2006, 16:05
You dont really need to worry about how the standard deviation is calculated.

Basically:

1) Find the mean of a set of numbers
2) Find the difference between each of the numbers and the mean
3) Square the differences and add them together
4) Take the positive square root of this value.

For this question you just need to find the mean = sum of all numbers/no. in set = 1000/10 = 100

100 - 22.4 = 77.6

The question asks how many of the values are below 77.6

= 2

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Manager
Joined: 25 Sep 2006
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07 Dec 2006, 20:52
I have a problem understanding the question.

how many of them are more than 1 sigma below mean

1 sigma below mean = 77.6 ok
MORE than 77.6 , there are eight of them!
_________________

livin in a prison island...

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Manager
Joined: 12 Jul 2006
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08 Dec 2006, 18:26
Only 70 and 75 are less than 77.6 (or more than one standard deviation below the mean.)
_________________

I think I can. I think I can. I think I can.

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Manager
Joined: 04 Feb 2004
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09 Dec 2006, 08:48
Explanation as above - 2 is the answer

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Senior Manager
Joined: 05 Oct 2006
Posts: 266

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Re: Std deviation gmat prep [#permalink]

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10 Dec 2006, 02:59
mean = 100
one std dev below, 100 - 22.4 = 77.6

only 2 values 70,75 are below 77.6.

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Re: Std deviation gmat prep   [#permalink] 10 Dec 2006, 02:59
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# Std deviation gmat prep

Moderator: chetan2u

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