Question

The incomes of trainees at a local mill are normally distributed with a mean of $1,100 and a standard deviation $150. what percentage of trainees earn less than $900 a month?

Answer 1

In this problem we are given the mean of $1100, SD of $150 and x equal to $900. In this case, we need to use the z-score table to answer the problem: 
z = (x-mean)/sd
z = (900-1100)/150
z = -1.33
from z-table, the probability at the left of z= -1.33 is equal to 9.18%