# 1.The distribution of a random variable X and the distribution of the sample average of X

Question

The distribution of a random variable X and the distribution of the sample average of X are the same.

True

False

1 points

QUESTION 2

Constructing a confidence interval involves computing the

probability of error.

margin of error.

standard deviation for the population.

test statistic.

1 points

QUESTION 3

When the confidence coefficient is .6, alpha is

1 points

QUESTION 4

When the confidence coefficient is .75, alpha is

1 points

QUESTION 5

If the sample size is 76 and the population standard deviation is 16.81 then the standard error is ? (Answer to two decimal places)

2 points

QUESTION 6

For a sample of 54 discount brokers the average price of a $5,000 trade was $33.77. Past surveys of this kind show a standard deviation of $15 so we assume that is the known population standard deviation. Construct a 90% confidence interval and enter the lower bound for the interval. (Answer to one decimal place and do not include a $ sign).

2 points

QUESTION 7

For a sample of 54 discount brokers the average price of a $5,000 trade was $33.77. Past surveys of this kind show a standard deviation of $15 so we assume that is the known population standard deviation. Construct a 90% confidence interval and enter the upper bound for the interval. Hint, your answer should be larger than the one for the previous question since they begin with the same summary data. (Answer to one decimal place and do not include a $ sign).

2 points

QUESTION 8

If there are 38 observations then how many degrees of freedom are there for the t distribution (for a sample mean)?

2 points

QUESTION 9

If there are 49 observations then how many degrees of freedom are there for the t distribution (for a sample mean)?

2 points

QUESTION 10

To construct a confidence interval for the population mean when the standard deviation is known we use a

z value.

t value.

F value.

alpha value.

2 points

QUESTION 11

To construct a confidence interval for the population mean when the population standard deviation is unknown, and therefore must be estimated, we use a

z value.

t value.

F value.

alpha value.

2 points

QUESTION 12

A 2009 sample of New York hotel room prices had an average of $273. Assume this was from a sample of 48 hotels. Assume also that the known standard deviation for the room rates is $72. Construct a 99% confidence interval and report the lower bound for the interval. (Answer to one decimal place and do not include a $ sign).

2 points

QUESTION 13

A 2009 sample of New York hotel room prices had an average of $273. Assume this was from a sample of 48 hotels. Assume that the known standard deviation is $72. Construct a 99% confidence interval and report the upper bound for the interval. Your number should be larger than for the previous problem. (Answer to one decimal place and do not include a $ sign).

2 points

QUESTION 14

If there are 26 df and the confidence coefficient or cc=.8 then the appropriate t value to use when constructing a confidence interval is (answer to three decimal places).

2 points

QUESTION 15

If there are 48 df and the confidence coefficient or cc=.95 then the appropriate t value to use when constructing a confidence interval is (answer to two decimal places).

2 points

QUESTION 16

Alpha is known as the power of a test.

True

False

1 points

QUESTION 17

Given the same data set, a wider confidence interval will have a larger margin of error.

True

False

1 points

QUESTION 18

To construct a confidence interval for the mean you will need

a point estimate.

the expected value from the underlying distribution.

the degrees of freedom.

a p-value.

1 points

QUESTION 19

When constructing a confidence interval for the mean, the choice of whether to use a t value or a z value depends on

the sample size.

whether or not sigma is known.

whether or not you are given the degrees of freedom.

the distribution of the variable for which you are estimating the mean.

2 points

QUESTION 20

If there are 52 observations in a sample, how many degrees of freedom are there? (The context here is for finding a t value when constructing a confidence interval or testing a hypothesis for the pupoulation mean).

1 points

QUESTION 21

To find the necessary sample size you need to know the acceptable margin of error.

True

False

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