A normal distribution

Question

A normal distribution hast=80 and sigma=10. What is the probability of randomly selecting a score greater than 90 from this distribution ?

Answer 1

mean = 80

standard deviation = 10

use the empirical rule: 68% are within 1 standard deviation of the mean. 32% out beyond 1 standard deviation of the mean, 32/2 = 16% is above 80+10 = 90

Probability of greater than 90 = 16%

or use a z score calculator on line to get a more accurate percent

15.866%. The empirical rule rounded it off to (100-68)/2=16%

or use a z table, on line or usually in the appendix of a statistics textbook.

or use a hand calculator with a statistics function