find the indicated probability

Question

P(greater than or equal to 120) mean is 100 and the standard deviation is 15

Answer 1

use standard normal probability table to determine probability.

use z = (x - mean)/SD transformation which is standard normal (mean = 0 , standard deviation = 1)

P(x > 120) = P(z > (120-100)/15) = P(z > 1.33) = P(z < -1.33) = 0.0918 (from standard normal probability table)