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# For an examination, a score of 58 was two standard

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Intern
Joined: 25 Aug 2008
Posts: 30
For an examination, a score of 58 was two standard [#permalink]

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14 Oct 2008, 15:44
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

For an examination, a score of 58 was two standard deviations below the mean and a score of 98 was three standard deviations above the mean. What was the mean score for the examination?

a. 74
b. 76
c. 78
d. 80
e. 82

Thanks.
Director
Joined: 23 May 2008
Posts: 806

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14 Oct 2008, 15:59
let the mean = y
let stand dev= x

y + 3x =98
y - 2x = 58

subtract second equation from first

5x=40, x=8

2(8) + 58 = 74

or

58-98=40

40 represents 5 standard deviations

so 40/5 =8

2(8) + 58 = 74
Senior Manager
Joined: 21 Apr 2008
Posts: 269
Location: Motortown

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14 Oct 2008, 16:03
A
Will go with the explanation of bigtreezl
SVP
Joined: 05 Jul 2006
Posts: 1747

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14 Oct 2008, 16:17
Poots wrote:
For an examination, a score of 58 was two standard deviations below the mean and a score of 98 was three standard deviations above the mean. What was the mean score for the examination?

a. 74
b. 76
c. 78
d. 80
e. 82

Thanks.

-A + 2S = -58
A+3S =98

5S = 40

S = 8

A = 74

A
Intern
Joined: 25 Aug 2008
Posts: 30

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14 Oct 2008, 17:11
Both explanations are great! Thanks so much.
Re: Standard Deviation   [#permalink] 14 Oct 2008, 17:11
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