stressedadfff
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hey guys does anyone know how to solve a and c? :0
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okayokay123
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You know the empirical or 68/95/99.7 rule? Basically 68% of scores is within 1 standard deviation from the mean (1 s.d above and below the mean), 97% within 2, and 99.7% within 3. 
For part a. you would need to work out how many standard deviations above or below the mean each of those scores are. So for a score >95, the score of 95 is 27 above the mean, or 3 standard deviations. So the values *greater* than 3 standard deviations above or below the mean is gonna be 100% - 99.7% = 0.3% of the cohort.
Now you only want to find the students above 3 standard deviations not below, so it would be 0.15% of students with a score more than 95.
0.0015x2000 = 3 students.
For question c. between 59 and 68 is 1 s.d below the mean and 2 s.d above the mean. Using the empirical rule, that ends up being 34+34+13.5 = 81.5% of students or 1630 students
For part a. you would need to work out how many standard deviations above or below the mean each of those scores are. So for a score >95, the score of 95 is 27 above the mean, or 3 standard deviations. So the values *greater* than 3 standard deviations above or below the mean is gonna be 100% - 99.7% = 0.3% of the cohort.
Now you only want to find the students above 3 standard deviations not below, so it would be 0.15% of students with a score more than 95.
0.0015x2000 = 3 students.
For question c. between 59 and 68 is 1 s.d below the mean and 2 s.d above the mean. Using the empirical rule, that ends up being 34+34+13.5 = 81.5% of students or 1630 students