# Question 1 David Lane: Page 364 Exercise 4 Why is a 99% confidence interval wider than a 95%…

Question 1 David Lane: Page 364 Exercise 4
Why is a 99% confidence interval wider
than a 95% confidence interval?

Question 2 David Lane: Page 365 Exercise 15
You take a sample of 22 from a
population of test scores, and the mean of your sample is 60.
You know the standard deviation of the
population is 10.

What is the point estimate for the
population mean?

What is the 99% confidence interval on
the population mean?

Now assume that you do not know the
population standard deviation, but the standard deviation in your sample is 10.
What is the 99% confidence interval on
the mean now?

What distribution did you use when
computing the first confidence interval?
What is the degrees freedom for
calculating the confidence interval?

What distribution did you use when
computing the second confidence interval?
What is the degrees freedom for calculating
the confidence interval?
Question 3 David Lane: Page 366 Exercise 18
You were interested in how long the
average psychology major at your college studies per night, so you asked 10
psychology majors to tell you the amount they study.
You were given the following study times:
2, 1.5, 3, 2,
3.5, 1, 0.5,
3, 2, 4.
The average study time from the above
data (Xbar) is 2.25
The standard deviation of the study
times from the above data is 1.11

What is the appropriate distribution for
finding a confidence interval?
What is the degrees of dreedom (dF)?
Find the 95% confidence interval on the
population mean.

Find the 90% confidence interval on the
population mean.

Question 4 Illowsky: Page 450 Exercise
100
What is meant by the term â€œ90%
confidentâ€ when constructing a confidence interval for a mean?
Question options:
Â·
If we took repeated
samples, approximately 90% of the samples would produce the same confidence
interval.
Â·
If we took repeated
samples, approximately 90% of the confidence intervals calculated from those
samples would contain the sample mean.
Â·
If we took repeated
samples, approximately 90% of the confidence intervals calculated from those
samples would contain the true value of the population mean.
Â·
If we took repeated
samples, the sample mean would equal the population mean in approximately 90%
of the samples.

Question 5 Illowsky: Page 452 Exercise
106
Suppose that a committee is studying
whether or not there is waste of time in our judicial system. It is interested
in the mean amount of time individuals waste at the courthouse waiting to be
called for jury duty. The committee randomly surveyed 81 people who recently
served as jurors. The sample mean wait time was eight hours with a sample standard
deviation of four hours.
. x Â¯
= 8
ii.
i Standard deviation = 4
iii. n = 81
iv. n â€“ 1 = 81 â€“ 1 = 80

Define the random variables X and X Â¯ by
selecting the appropriate letter below.

Which distribution should you use for
this problem?
Enter the degrees of freedom for this
problem =
Construct a 95% confidence interval for
the population mean time wasted.

What is meant by the term â€œ95%
confidentâ€ when constructing a confidence interval for a mean?

Question 6 Illowsky: Page 454 Exercise
112
In a recent sample of 84 used car sales
costs, the sample mean was \$6,425 with a standard deviation of \$3,156.
Assume the underlying distribution is
approximately normal.
Which distribution should you use for
this problem?
Enter the degrees of freedom (dF) for
this problem
Define the random variables X and X Â¯ by
selecting the appropriate letter below.

Construct a 95% confidence interval for
the population mean time wasted.

What is meant by the term â€œ95%
confidentâ€ when constructing a confidence interval for a mean?