The branch manager ofan outlet (Store I) ofa nationwide
chain of pet supply stores wants to study characteristics
of her customers. In particular, she decides to focus on
two variables: the amount of money spent by customers and
whether the customers own only one dog, only one cat, or
more than one dog and/or cat. The results from a sample of
70 customers are as follows:
• Amount of money spent: X $2 1.34, S $9.22.
• 37 customers own only a dog.
• 26 eustomers own only a cat.
• 7 customers own more than one dog and/or cat.
a. Construct a 95% confidence interval estimate for the
population mean amount spent in the pet supply store.
b. Construct a 90% confidence interval estimate for the
population proportion of customers who own only a cat.
The branch manager of another outlet (Store 2) wishes to
conduct a similar survey in his store. The manager does not
have access to the information generated by the manager of
Store I. Answer the following questions:
c. What sample size is needed to have 95% confidence of
estimating the population mean amount spent in this store
to within ± $1.50 if the standard deviation is estimated to
d. How many customers need to be selected to have 90%
confidence of estimating the population proportion of
customers who own only a cat to within ±0.045?
e. Based on your answers to (c) and (d),