Hoping to lure more shoppers downtown, a city builds a new public parking garage in the central business district. The city plans to pay for the structure through parking fees. For a random sample of

42

weekdays, daily fees collected averaged

$133,

with standard deviation of

$16.

Complete parts a through e below.

a) What assumptions must you make in order to use these statistics for inference?

Select all that apply.

A.

The distribution is unimodal and symmetric with no outliers.

B.

The data values should be dependent.

C.

The sample size is at least 10% of the population.

D.

The data are a random sample of all days.

b) Find a

90%

confidence interval for the mean daily income this parking garage will generate.

The

90%

confidence interval for the mean daily income is

($enter your response here,$enter your response here).

(Round to two decimal places as needed.)

c) Explain in context what this confidence interval means.

Choose the correct answer below.

A.

There is

90%

confidence that the daily income for all weekdays falls in the interval.

B.

There is

90%

confidence that the mean daily income will always fall in the interval.

C.

There is

90%

confidence that the interval contains the mean daily income.

D.

There is

90%

confidence that the daily income for a weekday falls in the interval.

d) Explain what

90%

confidence means in this context.

Choose the correct answer below.

A.

90%

of all weekdays sampled have daily incomes that fall in the interval.

B.

90%

of all weekdays have daily incomes that fall in the interval.

C.

90%

of all samples of size

42

have a mean daily income that is in the interval.

D.

90%

of all samples of size

42

produce intervals that contain the mean daily income.

e) The consultant who advised the city on this project predicted that parking revenues would average

$140

per day. Based on your confidence interval, what do you think of the consultant's prediction? Why?

Since the

90%

confidence interval

contains

does not contain

the predicted average, the consultant's prediction is

not plausible.

plausible.