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%

I got D.

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%


I got D.

anonymous · Answer

77 is one stdev away from the mean, 68

konradzuse · Answer

mhm

anonymous · Answer

through 68-95-99.7 rule, you know that from the mean to one stdev is 34%

anonymous · Answer

and everything below the mean is obviously 50%.

konradzuse · Answer

hmm

konradzuse · Answer

that woold mean C?

anonymous · Answer

so add those two numbers, and you get 84%, which is the percentage of people who got below 77

anonymous · Answer

yes.

anonymous · Answer

the answer you got is those who either got

anonymous · Answer

1. above 77
or

anonymous · Answer

2. below 59

konradzuse · Answer

I was looking at the 68 :P.

anonymous · Answer

thats why your answer (32%) is twice the actual answer (16%)

konradzuse · Answer

I realize thats a diff spread.

anonymous · Answer

yeah I see where you're coming from.

konradzuse · Answer

I'm really tired when I do math :P.

anonymous · Answer

stats is all about the wording of the question. not too much math. good luck with it :)

konradzuse · Answer

7 points 4 1 medal good stff :)

konradzuse · Answer

Oh yeah I hate it...  HW Q 1 was 2 parts 1,2 and part 2 asked aboot part 1 withoot saying it was LOL... :(