Question

Scores on a certain exam are normally distributed with a mean of 78 and a variance of 25. What is the score obtained by the top 5% of the students?

I do not understand the 5% part. What does the tail look like on the bell-shaped graph?

Answer 1

86.2? :D

Answer 2

Standard deviation (SD) = square root of variance

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (.05) related to the Z score. Insert the values into equation above and solve for the score.

http://www.regentsprep.org/regents/math/algtrig/ATS2/NormalLesson.htm