# 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?