Question

The manager of the service department of a local car dealership has noted that the service times of a sample of 15 new automobiles have a sample variance of S2 = 16.

A 95% confidence interval estimate for the population variance of service times for all their new automobiles is:

A 95% confidence interval estimate for the **population
standard deviation** of service times for all their new
automobiles is:

Answer #1

The manager of the service department of a local car dealership
has noted that the service times of a sample of 30 new automobiles
has a standard deviation of 7 minutes. A 99% confidence interval
estimate for the standard deviation of the service times for all
their new automobiles is 16.047 to 45.722 4.778 to 8.066 22.93 to
96.31 27.1520 to 108.299

Exhibit 4 (Questions 19-22)
The manager of the service department of a local car dealership
has noted that the service times of a sample of 15
new automobiles has a sample standard deviation of S =
4 hours. We are interested to test the following
hypotheses using α = 0.05 level of
significance:
H0 : σ2 ≤ 14
Ha : σ2 > 14
Refer to Exhibit 4. Assuming that the
population of service times follows an approximately normal
distribution, what...

Exhibit 4
The manager of the service department of a local car dealership has
noted that the service times of a sample of 15 new automobiles has
a sample standard deviation of S = 4 hours. We are interested to
test the following hypotheses using α = 0.05 level of
significance:
H0
: σ2 ≤ 14
Ha
: σ2 > 14
a. Refer to Exhibit 4. Assuming that the population of service
times follows an approximately normal distribution, what is...

Repair time (X) for an oil change at a car dealership has a
population mean of 50 min and a population standard deviation of 7
min. Questions A and B must be done using a pencil and
paper.
a.) If a random sample of 50 oil changes is
selected. Set up a 99% confidence interval estimate for an oil
change.
b.) If a random sample of 75 oil changes is
selected. Set up a 95% confidence interval estimate for an...

Sketching required.
7. A car dealership would like to estimate the mean mpg of
its new model car with 90% confidence. The population is normally
distributed; however we are taking a sample of 25 cars with a
sample mean of 96.52 and a sample standard deviation of 10.70.
Calculate a 90% confidence interval for the population mean using
this sample data.
Answers
Point Estimate
Standard Error
Margin of Error
Alpha
Critical Value
Confidence Interval

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