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Standard deviation and % ?

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Source: — Data Sufficiency |
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Re: Standard deviation and % ?

by iamcste » Sun May 17, 2009 10:03 am
California4jx wrote:can anyone provide explanation - OA: A
A


when data points are scaled or multipled by a constant, sdeviation is scaled or multipled by the same constant

here, after removing 30% of water from each tank, each tank has 0.7 of water hence standard deviation would be multipled by 0.7

since we know value of sd before removal of water, we can calculate sd after removal of water =0.7*10= 7 gallons

in stmt 2, we dont know the individual data points to calculate sd post removal of water
Last edited by iamcste on Sun May 17, 2009 10:05 am, edited 1 time in total.
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by cramya » Sun May 17, 2009 10:04 am
https://www.beatthegmat.com/gmat-prep-qu ... t2120.html
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by California4jx » Sun May 17, 2009 11:46 am
Thanks !! - very good link.
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Re: Standard deviation and % ?

by California4jx » Sun May 17, 2009 11:47 am
iamcste wrote:
California4jx wrote:can anyone provide explanation - OA: A
A


when data points are scaled or multipled by a constant, sdeviation is scaled or multipled by the same constant

here, after removing 30% of water from each tank, each tank has 0.7 of water hence standard deviation would be multipled by 0.7

since we know value of sd before removal of water, we can calculate sd after removal of water =0.7*10= 7 gallons

in stmt 2, we dont know the individual data points to calculate sd post removal of water
Thanks.
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