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MIDDLE EAST TECHNICAL UNIVERSITY – NORTHERN CYPRUS CAMPUS
BUS 152 STATISTICS FOR SOCIAL SCIENCES
SPRING 2011
STUDY SET: CONFIDENCE INTERVAL ESTIMATION
Problem 1.
The manager of a paint supply store wants to estimate the actual amount of
paint contained in 1gallon cans purchased from a nationally known manufacturer. It is
known from the manufacturer’s specifications that the standard deviation of the amount
of paint is equal to 0.02 gallon. A random sample of 50 cans is selected, and the sample
mean amount of paint per 1gallon can is 0.995 gallon.
a.
Construct a 99% confidence interval estimate of the population mean amount of paint
included in a 1gallon can.
b.
On the basis of your results, do you think that the manager has a right to complain to
the manufacturer? Why?
c.
Must you assume that the population amount of paint per can is normally distributed
here? Explain.
d.
Construct a 95% confidence interval estimate. How does this change your answer to
(b)?
Problem 2.
The
inspection
division
of
the
Lee
County
Weights
and
Measures
Department wants to estimate the actual amount of soft drink in 2liter bottles at the local
bottling plant of a large nationally known softdrink company. The bottling plant has
informed the inspection division that the population standard deviation for 2liter bottles
is 0.05 liter. A random sample of 100 2liter bottles at this bottling plant indicates a
sample mean of 1.99 liters.
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 Spring '11
 çeşmecibaşı
 Accounting, Normal Distribution, Standard Deviation, confidence interval estimate, standard normal table

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