In a survey of 1,000 people, 420 are opposed to the tax increase. Construct a 90 percent

confidence interval for the proportion of those people opposed to the tax increase.

A. [.394 .446]

B. [.380 .460]

C. [.389 .451]

D. [.399 .441]

What is the probability that a random variable having a standard normal distribution is

between .87 and 1.28?

A. .0919

B. .4100

C. .6517

D. .3483

If the scores on an aptitude test are normally distributed with mean 500 and standard

deviation 100, what proportion of the test scores are less than 585?

A. .1977

B. .8500

C. .1500

D. .8023

For a normal population with a mean of 100 and a variance 100, the P(X = 100) is ___.

A. 1.0

B. 0.5

C. 0.75

D. None of the above

If we have a sample size of 36 and the estimate of the population proportion is .90, the

standard deviation of the sampling distribution of the sample proportion is:

A. 0.0009

B. 0.05

C. 0.03

D. 9

Suppose that the waiting time for a license plate renewal at a local office of a state motor

vehicle department has been found to be normally distributed with a mean of 30 minutes and a

standard deviation of 8 minutes. What is the probability that a randomly selected individual will

have a waiting time between 15 and 45 minutes?

A. 1.00

B. .9699

C. .5000

D. .9392

What sample size is needed to estimate the population proportion within 1 percent using a 99

percent confidence level?

A. 6766

B. 9604

C. 11569

D. 16590

It has been reported that the average time to download the home page from a government

website was 0.9 seconds. Suppose that the download times were normally distributed with a

standard deviation of 0.3 seconds. If random samples of 36 download times are selected, what is

the probability that the sample mean will be more than 0.84 seconds?

A. .1151

B. .4522

C. .8849

D. .5478

The life of a light bulb is exponentially distributed with a mean of 1,000 hours. What is the

probability that the bulb will last:

More than 1,200 hours?

A. .3012

B. .3679

C. .4345

D. .6988

A study shows that employees that begin their work day at 9:00 a.m. vary their times of arrival

uniformly from 8:40 a.m. to 9:30 a.m. The probability that a randomly chosen employee reports

to work between 9:00 and 9:15 is:

A. 40%

B. 30%

C. 20%

D. 10%

The next question are based on the following paragraph.

A large hospital wholesaler, as part of an assessment of workplace safety, gave a random sample

of 54 of its warehouse employees a test (measured on a 0 to 100 point scale) on safety procedures.

For that sample of employees, the mean test score was 75 points, with a sample standard deviation

of 15 points. Determine and interpret a 95% confidence interval for the mean test score of all the

company's warehouse employees.

To construct the 95% confidence interval, we should:

A. use t-value 1.669 from the t table, because we have the sample standard deviation.

B. use t-value 2.006 from the t table, because we have the sample standard deviation.

C. use z-value 2.576 from the z table, because we have the population standard deviation.

D. use z-value 1.960 from the z table, because we have the population standard deviation