Scores on a university exam are Normally distributed with a mean of 68 and a standard deviation of 9. Using the 68-95-99.7 rule, what percentage of students score above 77?
A. 2.5%
B. 5%
C. 16%
D. 32%

confused on what equation i use to get the answer ?

Question

Scores on a university exam are Normally distributed with a mean of 68 and a standard deviation of 9. Using the 68-95-99.7 rule, what percentage of students score above 77?
A.	2.5%
B.	5%
C.	16%
D.	32%

confused on what equation i use to get the answer ?

dape · Answer

No equation is needed if you know the 68-95-99.7 rule. Since 77 is one standard deviation above 68 (68+9=77), we know from the rule and some sketching that 16% must be the right answer, see my drawing.
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