Question

Mean=121

Standard Deviation=9
Find P(x>1103)
97.5%
0.5%
68%
95%

Answer 1

97.5%

Explanation:

Find the z-score.

z = (x − μ) / σ

z = (103 − 121) / 9

z = -2

We can use a table or calculator to find the probability:

P(Z > -2) = 0.975

Alternatively, we can use the Empirical rule. 95% of the normal distribution is between -2 and +2 standard deviations. Since a normal distribution is symmetrical, 47.5% is between -2 and 0. 50% is greater than 0. So the percent greater than -2 is 47.5% + 50% = 97.5%.