A company is interested in estimating , the mean number of days of sick leave taken

by its employees. The firm's statistician randomly selects 100 personnel files and notes the

number of sick days taken by each employee. The sample mean is 12.2 days and the sample

standard deviation is 10 days. How many personnel files would the director have to select in

order to estimate to within 2 days with a 99% confidence interval?

A. 2

B. 13

C. 136

D. 165

E. 166

The state highway department is studying traffic patterns on one of the busiest highways

in the state. As part of the study, the department needs to estimate the average number of

vehicles that pass an intersection each day. A random sample of 64 days gives us a sample

mean of 14,205 cars and a sample standard deviation of 1,010 cars. After calculating the

confidence interval, the highway department officials decide that the precision is too low for

their needs. They feel the precision should be 300 cars. Given this precision, and needing to

be 99% confident, how many days do they need to sample?

A. 109

B. 76

C. 75

D. 62

E. 9

According to data from the state blood program, 40% of all individuals have group A blood. If six (6) individuals give blood, find the probability At least 3 of the individuals have group A blood.

A. .8208

B. .5443

C. .4557

Suppose that x has a hypergeometric distribution with N = 10, r = 5 and n = 3. Calculate the standard deviation of the distribution.

A. 0.583

B. 0.764

C. 1.500

D. 0.778

D. .1792

A large disaster cleaning company estimates that 30% of the jobs it bids on are finished within the bid time. Looking at a random sample of 8 jobs that is has contracted: Calculate the probability that exactly 4 of the jobs were not completed within the bid time.

A. .0081

B. .2401

C. .0113

D. .1361

A lawyer believes that the probability is .3 that she can win a discrimination suit. If she wins the case she will make $40,000, but if she loses she gets nothing. Assume that she has to spend $5000 preparing the case. What is her expected gain?

A. $35,000

B. $7,000

C. $10,500

D. $9,000

During off hours, cars arrive at a tollbooth on the East-West toll road at an average rate of

0.5 cars per minute. The arrivals are distributed according to the Poisson distribution.

What is the probability that during the next five minutes three cars will arrive?

A. .2138

B. .1804

C. .0126

D. .0613

Historical data shows that the average number of patient arrivals at the intensive care unit of General Hospital is 3 patients every 2 hours. Assume that the patient arrivals are distributed according to Poisson distribution. Determine the probability of at least 4 but no more than 8 patients arriving in a three-hour period.

A. .3813

B. .5711

C. .4276

D. .7861

E. .6174

Historical data shows that the average number of patient arrivals at the intensive care unit of General Hospital is 3 patients every 2 hours. Assume that the patient arrivals are distributed according to Poisson distribution. Determine the probability of 6 patients arriving in a five-hour period.

A. .136

B. .109

C. .246

D. .001