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standard deviation

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by rahul.s » Mon Feb 08, 2010 8:34 am
the class mean score on a test was 60, and the standard deviation was 15. if elena's score was within 2 standard deviations of the mean, what is the lowest score she could have received?

[spoiler]OA: 30[/spoiler]

how?
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by Osirus@VeritasPrep » Mon Feb 08, 2010 8:36 am
Subtract 15 twice from the average. The standard deviation was 15. And the average was 60. If her score was 2 standard deviations from the average then her score would be within the range of 30- 100
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by rahul.s » Mon Feb 08, 2010 8:41 am
so 2 standard deviations within the mean of 60 = 30. is it a formula?

example: if the mean is 50, and the standard deviation is 5, then 3 standard deviations within the mean = 35. is it?
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by Osirus@VeritasPrep » Mon Feb 08, 2010 8:42 am
rahul.s wrote:so 2 standard deviations within the mean of 60 = 30. is it a formula?

example: if the mean is 50, and the standard deviation is 5, then 3 standard deviations within the mean = 35. is it?
Yes. however many standard deviations you are looking for just multiply that number by the standard deviation.
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