Stats test #6

The number of tickets purchased by a customer for a musical performance at a certain concert hall can be considered a random variable. The table below shows the relative frequency distribution for the number of tickets purchased by a customer. (# of tickets:relative frequency) (1:.2)(2:.45)(3:.1)(4:.2)(5:.05) Suppose each ticket for a musical performance cost $12. Based on the distribution shown, what is the mean cost per customer for the performance?

$29.40

In a certain school, 17 percent of the students are in enrolled in a psychology course. 28 percent of students are enrolled in a foreign language course, and 32 percent of people are enrolled in either a psychology course of a foreign language course or both. What is the probability that a student chosen at random from this school will be enrolled in both a foreign language course and a psychology course?

0.13

For flights from a particular airport in January, there is a 30 percent chance of a flight being delayed because of icy weather. If a flight is delayed because of icy wether, there is a 10 percent chance the flight will also be delayed because of a mechanical problem. If a flight is not delayed because of icy weather, there is a 5 percent chance that it will be delayed because of a mechanical problem. If one flight is selected at random from the airport in January, what is the probability that the flight selected will have at least one of the two types of delays?

0.335

The following table shows the probability distribution for the number of books a student typically buys at the annual book fair held at an elementary school. ( # of books:probability) (0:.35)(1:.20)(2:.15)(3:.10)(4:.07)(5:.08)(6:.04)(7:.01) Let the random variable B represent the number of books a student buys at the next book fair. What is the expected value of B?

1.79

Ninety percent of the people who have a paerticular disease will have a positive result on a given diagnostic test. Ninety percent of the people who do not have the disease will have a negative result on the test. If 5 percent of a certain population has the disease, what percent of that population will test positive for the disease?

14%

Each value in a sample has been transformed by multiplying 3 and then adding 10. If the original sample had a variance of 4, what is the variance of the transformed sample?

36

Ali surveyed 200 students at a school and recorded the eye color and gender of each student. Of the 80 male students who were surveyed, 60 had brown eyes. If eye color and gender are independent, how many female students surveyed would be expected to have brown eyes?

90

A manufacturer makes lightbulbs and claims that their reliability is 98 percent. Reliability is defined to be the proportion fo non-defective items that are produced over the long term. If the company's claim is correct, what is the expected number of non-defective lightbulbs in a random sample of 1,000 lightbulbs?

980

Events D and E are independent, with P(D)=0.6 and P(D and E)=0.18. Which of the following is true?

P(D or E) = .72

A nonprofit organization plans to hold a raffle to raise funds for its operation. A total of 1,000 raffle tickets will be sold for $1.00 each. After all the tickets are sold, one ticket will be selected at random and its owner will receive $50.00. The expected value for the net gain for each ticket is -$0.95. What is the meaning of the expected value in this context?

The ticket owners lose an average of $0.95 per raffle ticket.