[jcwgosooners]

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 percent of students score above 77?

[ebaines]

Note that a score of 77 is 9 points above the mean. And since the standard deviation of scores ins 9 points, this means a score of 77 is one standard deviation above the mean. The "68-95-99.7 rule" refers to the percentage of the population that are less than 1, 2 and 3 standard deviations above the mean. The question essentially asks what percentage lies above 1 standard deviation. Can you finish this now?

[jcwgosooners]

No lol

[jcwgosooners]

Would it be 2.5?

[ebaines]

Would it be 2.5?

How did you get 2.5?

You know that 68% of the population has a score of 77 or less. So what percent of the population has a score above 77?

[jcwgosooners]

So its 32?

[ebaines]

So its 32?

Bingo!