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# Standard deviation question watch

1. help Please ! i have the answer, it's 16%, but can you explain how we arrive to this this conclusion ? here is the question ; If a student's grade is 65 where the mean is 55 and the standard deviation 10, then the proportion of student who will score higher than 65 is about : a)34% b)68% c)16% d)2,5%

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2. (Original post by Sashare)
help Please ! i have the answer, it's 16%, but can you explain how we arrive to this this conclusion ? here is the question ; If a student's grade is 65 where the mean is 55 and the standard deviation 10, then the proportion of student who will score higher than 65 is about : a)34% b)68% c)16% d)2,5%
Posted from TSR Mobile

Posted from TSR Mobile
Let X denote the score of a student.

Therefore ...
3. (Original post by Sashare)
help Please ! i have the answer, it's 16%, but can you explain how we arrive to this this conclusion ? here is the question ; If a student's grade is 65 where the mean is 55 and the standard deviation 10, then the proportion of student who will score higher than 65 is about : a)34% b)68% c)16% d)2,5%

Posted from TSR Mobile

Posted from TSR Mobile
If you know that the distribution is Normal (or can assume this) you should know a standard result that says that about 68% of the distribution lies within 1 standard deviation of the mean.

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