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# Need help with a calcul ! 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%

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1. It's strictly impossible to tell the answer without knowing how the scores are distributed, but here, it's clear that they are assuming a normal distribution

2. For a normal distribution, roughly 68% of all values lie within 1 standard deviation from the mean - that means that 100%-68%=32% lie more than 1 standard deviation from the mean. You should now be able to figure out where 16% comes from. (Hint: values can be both lower and higher than the mean, and a normal distribution is symmetric about its mean)

3. Minor point: It's "calculation", not "calcul"
3. This seems to be a duplicate post!
4. in a normal distribution there are about 68% of data within one standard deviation of the mean
5. (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
You may have heard of the 68-95-99.7 rule, being approximately the percentage of normally-distributed random data within 1/2/3 standard deviations of the mean.

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