At a large dept. store, the avg. number of years of employment for a cashier is 5.7 with a standard deviation of 1.8 years. If the number of years of employment at this department store is normally distributed, what is the probability that a cashier selected at random has worked at the store for over 10 years?

Question

At a large dept. store, the avg. number of years of employment for a cashier is 5.7 with a standard deviation of 1.8 years.  If the number of years of employment at this department store is normally distributed, what is the probability that a cashier selected at random has worked at the store for over 10 years?

MathMate · Answer

Calculate the Z-score:
Z=(10-5.7)/1.8=2.39
Look up the normal distribution table for the corresponding probability for LESS than 10 years, subtract this probability from 1.0 to get the probability of service of 10 years or more.

Table link:
http://www.math.unb.ca/~knight/utility/NormTble.htm