# Statistics of normal graph

**Question description**

1. **The
Management at Ohio National Bank does not want its customers to wait in line
for service for too long. The manager of a branch of this bank estimated that
the customers currently have to wait an average of 8 minutes for service. Assume
that the waiting times for all customers at this branch have a normal
distribution with a mean of 8 minutes and a standard deviation of 2 minutes**.

What is the probability that customers have to wait for 4 to 8 minutes?

Instructions: Show all steps:

a. Draw the normal curve and indicate the mean, standard deviation, and the X bar scale

b. Identify the area of interest (that is shade the area under the curve that you will compute the probability).

c. Covert the X bar values in Z scores

d. Look up the Z standardized table for the cumulative area(s).

e. Now, make your decision ( that a customer will have to wait for 4 to 8 minutes)

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