1. In constructing a confidence interval, s is used as an estimate of the population variance.

	True
	False

2. The critical value used for a 99% confidence interval for a sample mean when the population standard deviation is known is 2.58.

	True
	False

3. The researchers are not satisfied with their confidence interval and want to complete another study to find a shorter confidence interval. What should they change to ensure they find a shorter confidence interval?

	They should increase their confidence level and increase their sample size.
	They should increase their confidence level but decrease their sample size.
	They should decrease their confidence level but increase their sample size.
	They should decrease their confidence level and decrease their sample size.

4. Decreasing the sample size, while holding the confidence level the same, will do what to the length of your confidence interval?

	make it bigger
	make it smaller
	it will stay the same
	cannot be determined from the given information

5. When testing for differences between the means of two related populations, what is the null hypothesis?

	The difference between the population means is equal to 0.
	The difference between the population means is equal to 1.
	The difference between the population means is greater than 1.
	The difference between the population means is greater than 0.

6. A Type I error occurs when we

	correctly fail to reject a false null hypothesis.
	correctly reject a false null hypothesis.
	incorrectly reject a false null hypothesis.
	incorrectly reject a true null hypothesis.

7. A statistician wishes to determine the difference between two population means. A sample of 10 items from Population #1 yields a mean of 185 with a standard deviation of 20. The sample of 12 items from Population #2 yields a mean of 200 with a standard deviation of 25. Assume that the values are normally distributed in each population. How many degrees of freedom are there for this test?

	11
	20
	22
	21