b.
What is the probability that for each firm the sample mean
will be within 25 of the population mean μ (to 4 decimals)?

10. Refer to the Scheer Industries example in Section 8.2.

Use 6.82 days as a planning value for the population standard
deviation.
a. Assuming 95% confidence, what sample size would be
required to obtain a margin of error of 1 days (round up to
the next whole number)?
b. Assuming 90% confidence, what sample size would be
required to obtain a margin of error of 3 days (round up to
the next whole number)?
Top of Form
11. Health insurers are beginning to offer telemedicine
services online that replace the common office visit.
Wellpoint provides a video service that allows subscribers to
connect with a physician online and receive prescribed
treatments (
Bloomberg Businessweek
(March 4 – March 9, 2014). Wellpoint claims that users
of its LiveHealth Online service saved a significant amount

of money on a typical visit. The data shown below ($), for a
sample of 20 online doctor visits, are consistent with the
savings per visit reported by Wellpoint.
Assuming the population is roughly symmetric, construct
a 95% confidence interval for the mean savings for a televisit
to the doctor as opposed to an office visit (to 2 decimals).
95% confidence interval: $ to $ per visit
Top of Form
12. The president of Doerman Distributors, Inc., believes
that 33% of the firm's orders come from first-time customers.
A simple random sample of 100 orders will be used to
estimate the proportion of first-time customers.
a.
Assume that the president is correct and

p
= 0.33. What is the sampling distribution of p for this
study?

What is the probability that the sample proportion will be
between .26 and .40 (to 4 decimals)?
c.
What is the probability that the sample proportion will be
between .31 and .35 (to 4 decimals)?
Top of Form
13. The range for a set of data is estimated to be 68.
a.

What is the planning value for the population standard
deviation?
At 95% confidence, how large a sample would provide a

margin of error of 4?
At 95% confidence, how large a sample would provide a

margin of error of 2?

14. The following data are from a simple random sample.
4, 9, 13, 6, 13, 15
a.

What is the point estimate of the population mean?

What is the point estimate of the population standard
deviation (to 1 decimal)?

15. The average cost per night of a hotel room in New
York City is $266 (

, March 2009). Assume this estimate is based on a
sample of 45 hotels and that the sample standard deviation is
$60.
a.
With 95% confidence, what is the margin of error?
Round your answer to the nearest dollar.

$
b.
What is the 95% confidence interval estimate of the
population mean? Round your answers to the nearest dollar.
to
c.
Two years ago the average cost of a hotel room in New
York City was $229. Discuss the change in cost over the two-
year period.
Bottom of Form
Bottom of Form
Bottom of Form
Bottom of Form

Bottom of Form
Bottom of Form
Bottom of Form
Bottom of Form
Bottom of Form
Bottom of Form
Bottom of Form
Bottom of Form
Bottom of Form

Bottom of Form
- Select your answer -
- Select your answer -
- Select your answer -
- Select your answer -
- Select your answer -

- Select your answer -
Select
- Select your answer -