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Telephone Probability

Question 1

Assume that you are the owner of a small business that employs two people
on a telephone help desk. Records show that one of the employees is busy
taking calls for 40% or the time and the other is busy taking calls 55% of the

a) What is the probability that when a new call comes in that both of the
employees are busy on the telephone?

b) What is the probability that at least one of the employees will be

Question 2

Venture capital investments tend to be risky investments with a large
proportion of investments being unsuccessful. Suppose that you are the
manager of a venture capital firm with 20 investments. Assuming that it is
known that 70% of venture capital investments will be unsuccessful, determine
the following:

a) The probability that at least 5 of your investments will be successful.

b) The probability that no more than 15 will be unsuccessful.

Question 3

Suppose that 22% of employees in Australia intend to change employers over
the next two years. A company interested in reasons for their employee
turnover randomly samples a number of their employees:

a) If the company randomly samples 20 employees, find the probability
that exactly 4 of them will leave within two years.

b) For a random sample of 20 employees, find the mean, the variance
and the standard deviation for the number of employees that intend to
change employers of the next two years.


Solution Summary

The solution discusses probabilities in business.