The marks obtained by students of a class in a test are normally distributed with a mean of 60 marks and a standard deviation of 5 marks.

About what percent of students have scored more than 65 marks?

Question

The marks obtained by students of a class in a test are normally distributed with a mean of 60 marks and a standard deviation of 5 marks.
 
About what percent of students have scored more than 65 marks?

amistre64 · Answer

seems to be implying the empirical rule.  Do you recall the emiprical rule of thumb?

anonymous · Answer

no

amistre64 · Answer

then you are ill prepared for the solution.

amistre64 · Answer

the empirical rule informs us about 3 conditions with regards to standard deviations from the mean:

68% is within 1 sd of the mean
95% is within 2 sd of the mean
99% is within 3 sd of the mean

its also good to recall that the mean splits the distribution 50-50

anonymous · Answer

oh ok thanks i dont really understands this kind of math

amistre64 · Answer

at this point, its just memorization :)  we are essentially looking at this setup

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