Business Statistics II – STAT222
Summer 2015
(Due on 12/8/2015)
Name: 1-___________________________________________ Student ID ________________
2-___________________________________________ Student ID ________________
3-___________________________________________ Student ID ________________
4-___________________________________________ Student ID ________________


This homework is a group homework (group of 4 students maximum)
It counts for 5% of your total grade.
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Question One: Read the Problem [2 points]
A real estate agent believes that home with swimming pools take longer to sell than home without
swimming pools. A random sample of each type of recently sold homes was taken where the number of
days on the market is recorded. Results are:
Sample mean
Sample Standard deviation
Sample size

Homes with pool
77 days
8.4 days

Homes without pool
65 days
7.2 days

Assuming that the populations are normally distributed:
a. [1 point] What assumption we can make about the population variances: equal or unequal?
Interpret your results?

b. [1 point] Conduct the appropriate hypothesis test to determine if the real estate agent is correct. Use
the 0.05 level of significance.

Question Two: Read the Problem [2 points]
A maker of toothpaste is interested in testing whether the proportion of adults (over age 18) who use its
toothpaste and have no cavities within a six-month period is any different from the proportion of children
(18 and under) who use the toothpaste and have no cavities within a six-month period. To test this, it has
selected a sample of adults and a sample of children randomly from the population of those customers who
use their toothpaste. The following results were observed.
Sample size
Number with 0 cavities



a. [1 point] Based on these sample data and using a significance level of 0.05, what conclusion should
be reached? What is the p-value.


[1 point] Develop and interpret the desired 95 percent confidence interval estimate.

Question Three: Read the Problem [1 points]
Random samples from two normal populations produced the following statistics:
?? = 10
?? =10

?? = 28
?? =19

a. [1 point] Estimate with 95% confidence the ratio of the two population variances.

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