The branch manager ofan outlet (store i) ofa nationwide chain of pet

Question 8.73

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

be $10?

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),