Question

QUESTION 21

If we change a 90% confidence interval estimate to a 99% confidence interval estimate while holding sample size constant, we can expect

	a.	the width of the confidence interval to increase.
	b.	the width of the confidence interval to decrease.
	c.	the width of the confidence interval to remain the same.
	d.	the sample size to increase.

QUESTION 22

Which one of the following is a correct statement about the probability distribution of a t random variable?

	a.	The mean is zero but the standard deviation is greater than 1.
	b.	The mean and standard deviation can be any number.
	c.	The mean is zero but the standard deviation is less than 1.
	d.	The mean is zero and the standard deviation is 1.

QUESTION 23

A professor finds that for 16 randomly selected students the time needed to complete an assignment had a sample mean of 66 minutes and a sample standard deviation of 40 minutes. If the time needed to complete the assignment is normally distributed, then the standard error of the mean is

	a.	5
	b.	20
	c.	16
	d.	10

QUESTION 24

A professor finds that for 16 randomly selected students the time needed to complete an assignment had a sample mean of 65 minutes and a sample standard deviation of 40 minutes. If we need to develop an interval estimate of the mean, the appropriate distribution to use is:

	a.	the Z distribution
	b.	the t distribution
	c.	the normal distribution
	d.	none of the above

QUESTION 25

Suppose professor finds that for 16 randomly selected students the time needed to complete an assignment had a sample mean of 65 minutes and a sample standard deviation of 40 minutes. The 98% confidence interval estimate for the population mean is:

Please show your work. I may be able to give you partial credit even if your final answer is not correct.

QUESTION 26

After estimating the interval in the previous question, we can interpret it as:

	a.	We are 98% confident that the sample mean falls into the estimated interval.
	b.	We are 98% confident that the estimated interval contains the population mean.
	c.	We are 98% confident that the estimated interval contains the sample mean.
	d.	We are 98% confident that the true mean falls into the estimated interval.

QUESTION 27

For two unbiased point estimators of the same parameter, the point estimator with the smaller variance is said to have

	a.	smaller relative efficiency
	b.	smaller relative consistency
	c.	greater relative efficiency
	d.	greater relative consistency

QUESTION 28

When sample size gets larger, an unbiased point estimator gets closer and closer to the parameter it estimates. This property is called:

	a.	consistency
	b.	relative estimation
	c.	efficiency
	d.	unbiased efficiency

QUESTION 29

X-bar is an unbiased estimator of µ because

	a.	standard error of X-bar equals sigma/ square root of n
	b.	expected value of X-bar equals µ
	c.	shape of distribution of X-bar is normal.
	d.	Expected value of X-bar is greater than 1.

Answer 1