1. A production company’s 350 hourly employees average 37.6 years of age, with a standard deviation
of 8.3 years. If a random sample of 45 hourly employees is taken, what is the probability that the sample
will have an average age of less than 40 years?
2. Suppose a subdivision on southwest side of Denver, Colorado, contains 1,500 houses. The subdivision
was built in 1983. A sample of 100 houses is selected randomly and evaluated by an appraiser. If the
mean appraised value of a house in this subdivision for all houses is $177,000, with a standard deviation
of $8,500, what is the probability that the sample average is greater than $185,000?
3. Suppose 60% of the electrical contractors in a region use a particular brand of wire. What is the
probability of taking a random sample of size 120 from these electrical contractors and finding that .50
or less use that brand of wire?
4. If 10% of a population of parts is defective, what is the probability of randomly selecting 80 parts and
finding that 12 or more parts are defective?
5. According to a survey, 48% of executives believe that employees are most productive on Tuesday.
Suppose 200 executives are randomly surveyed:
a. what is the probability that fewer than 90 of the executives believe employees are most productive
on Tuesdays.
b. What is the probability that more than 100 of the executives believe employees are most productive
on Tuesdays.
6. The average cost of a one bedroom apartment in town is $550 per month. What is the probability of
randomly selecting a sample of 50 one bedroom apartments in this town and getting a sample mean of
less than $530 if the population standard deviation is $100?
7. According to the U.S. bureau of labor statistics, 20% of all people 16 years of age or older do
volunteer for work. Women volunteer slightly more than men, with 22% of women volunteering and
19% of men volunteering. What is the probability of randomly sampling 140 women 16 years of age or
older and getting 35 or more who do volunteer work? What is the probability of getting 21 or fewer
from this group? Suppose a sample of 300 men and women 16 years of age or older is selected
randomly from the US population. What is the probability that the sample proportion of those who do
volunteer work is between 18% and 25%?
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