Quiz about Spring Final Exam Review

Question 1

If P(A) = 0.5, P(B) = 0.6, P(A and B) = 0.1, what is P(A|B)?

Accepted Answer

1/6

Answer

1/2

Answer

3/10

Answer

1/5

Question 2

If P(A) = 0.30, P(A or B) = 0.40, and P(A and B) = 0.10, what is P(B)?

Accepted Answer

0.2

Answer

0.6

Answer

0.5

Answer

0.4

Answer

0.33

Question 3

Question 3.

Accepted Answer

0.284

Answer

0.311

Answer

0.579

Answer

0.612

Question 4

In a certain town, 50% of the households own a cellular phone, 40% own a pager, and 20% own both a cellular phone and a pager. The proportion of households that own neither a cellular phone nor a pager is:

Accepted Answer

30%

Answer

90%

Answer

0%

Answer

70%

Answer

10%

Question 5

Insurance company records indicate that 12% of all teenage drivers have been ticketed for speeding and 9% for going through a red light. If 4% have been ticketed for both, what is the probability that a teenage driver has been issued a ticket for speeding but not for running a red light?

Accepted Answer

8%

Answer

3%

Answer

12%

Answer

13%

Answer

17%

Question 6

Steven has a box of LED's containing 2 blue ones, 3 white ones, 7 red ones, and 3 green ones. If two LED's are drawn at random from the box without replacement, what is the probability that both LED's are not red?

Accepted Answer

4/15

Answer

56/225

Answer

23/30

Answer

64/224

Answer

11/15

Question 7

Which one of these variables is a continuous random variable?

Accepted Answer

the time it takes a randomly selected student to complete an exam.

Answer

the number of tattoos a randomly selected person has.

Answer

the number of women taller than 68 inches in a random sample of 5 women.

Answer

the number of correct guesses on a multiple choice test.

Question 8

The mean number of customers that make a purchase during the first hour that the store is open is:

Accepted Answer

3.0

Answer

2.0

Answer

4.0

Answer

2.9

Answer

2.5

Question 9

The standard deviation of the number of customers that make a purchase during the first hour that the store is open is:

Accepted Answer

1.4

Answer

4.0

Answer

3.0

Answer

0.2

Answer

2.0

Question 10

According to a CBS/New York Times poll, 15% of the public have responded to a telephone call-in poll. In a random group of five people, what is the probability that exactly two have responded to a call-in poll?

Accepted Answer

0.138

Answer

0.165

Answer

0.300

Answer

0.835

Answer

0.973

Question 11

Find the probability that x = 5

Accepted Answer

0.47

Answer

0.53

Answer

2.65

Answer

2.35

Answer

0.16

Question 12

A tax preparation firm wants to estimate the proportion of all taxpayers who wait until the last day to file their taxes. A group of 1000 taxpayers were randomly selected. The results reveal that 100 of them didn't file until the last day. Based on this sample, a 95% confidence interval for p, the proportion of taxpayers who wait until the last day to file their taxes, is (0.08, 0.12). What is the margin of error?

Accepted Answer

0.02

Answer

0.01

Answer

0.04

Answer

0.10

Question 13

A publishing company is studying the sales of various franchises in their chain of stores. They draw a random sample of 75 stores in the chain and measure the average daily sales. They find the mean daily sales to be $5,670, with a standard deviation of $1,750. Calculate a 90% confidence interval for the true mean daily sales of their stores.

Accepted Answer

($5333.40, $6006.50)

Answer

($2791.30, $8548.80)

Answer

($5149.50, $6190.50)

Answer

(5410.90, $5929.10)

Question 14

In a survey funded by Burroughs-Welcome, 750 of 1000 adult Americans said they didn't believe they could come down with a certain disease. Construct a 95% confidence interval estimate for the true proportion of adult Americans who don't believe they can contract the disease.

Accepted Answer

(0.723, 0.777)

Answer

(0.728, 0.772)

Answer

(0.718, 0.782)

Answer

(0.713, 0.787)

Question 15

Which of the following is a valid interpretation of a confidence interval?

Accepted Answer

We are 95% confident that the average number of credit hours per semester of students at the university falls in the interval 14.089 to 14.511 hours.

Answer

95% of the students take between 14.089 and 14.511 credit hours per semester.

Answer

We are 95% confident that the average number of credit hours per semester of the sampled students fall in the interval 14.089 to 14.511 hours.

Answer

The probability that a student takes 14.089 to 14.511 credit hours in a semester is 0.95.

Question 16

Suppose some researchers have created a confidence interval and wish to decrease the width of their interval. What are the two ways in which this can be accomplished?

Accepted Answer

Increase the sample size

Decrease the confidence level

Answer

Decrease the sample size

Decrease the confidence level

Answer

Increase the sample size

Increase the confidence level

Answer

Decrease the sample size

Increase the confidence level

Question 17

In the computation of a confidence interval, if the sample size is not changed but the confidence level is changed from 99% to 95%, you can expect

Accepted Answer

an interval that is narrower

Answer

an interval that is the same width since the sample size has not changed

Answer

an interval with the same width since the mean has not changed

Answer

an interval that is wider

Answer

the change cannot be determined from the information given

Question 18

Experiments on learning in animals sometimes measure how long it takes mice to find their way through a maze. The mean time is 18 seconds for one particular maze. A researcher thinks that a loud noise will cause the mice to complete the maze faster. She measures how long each of 10 mice takes with a noise stimulus. The appropriate hypotheses for this test are:

Accepted Answer

Question 19

In each of the following, the p-value and the significance level (alpha) are given for a hypothesis test.

Which pair of values warrants a rejection of the null hypothesis?

Accepted Answer

p-value = 0.0411

alpha = 0.05

Answer

p-value = 0.0312

alpha = 0.01

Answer

p-value = 0.0529

alpha = 0.05

Answer

p-value = 0.1328

alpha = 0.10

Question 20

The process of producing pain-reliever tables yields tablets with varying amounts of the active ingredient. It is claimed that the average amount of active ingredient per tablet is at least 200 milligrams. The Consumer Watchdog Bureau suspects that the company is shortchanging customers and tests a random sample of 70 tablets. The mean content of the active ingredient for this sample is 194.3 milligrams, with a standard deviation of 21 milligrams. What is the approximate p-value for the significance test?

Accepted Answer

0.013

Answer

0.050

Answer

0.488

Answer

0.100

Answer

0.024

Question 21

A hypothesis test was conducted concerning p = the proportion of all drivers who use high-octane gasoline. The null hypothesis was Ho: p = 0.14, the alternative hypothesis was Ha: p > 0.14, and the P-value was 0.2588. What conclusion should be made?

Accepted Answer

Fail to reject Ho.

There is not convincing evidence that p is greater than 0.14.

Answer

Reject Ho.

There is convincing evidence that p is greater than 0.14.

Answer

Accept Ho.

There is not convincing evidence that p is greater than 0.14.

Answer

Fail to reject Ha.

There is convincing evidence that p is greater than 0.14.

Question 22

A service station advertises that its mechanics can change a muffler in only 15 minutes. A consumer group believes it is slower and runs a hypothesis test using 49 cars needing new mufflers. In this sample, the mean changing time is 16.25 minutes with a standard deviation of 3.5 minutes. Is this strong evidence against the 15-minute claim? (In other words, would you reject Ho?)

Accepted Answer

Yes, because the p-value is 0.0079

Answer

Yes, because the p-value is 2.5

Answer

No, because the p-value is 0.0079

Answer

No, because the p-value is 0.9921

Question 23

Bages of a certain brand of tortilla chips claim to have a net weight of 14 ounces. A consumer advocacy group wishes to see if there is any evidence that the mean net weight is less than advertised.

They select 16 bags of this brand at random and finds the net weight of each. They find the the sample mean to be 13.88 oz with a standard deviation of 0.24 oz. Based on this data, we would:

Accepted Answer

Reject Ho at alpha = 0.05, but not at 0.025

Answer

Reject Ho at alpha = 0.10, but not at 0.05

Answer

Reject Ho at alpha = 0.025, but not at 0.01

Answer

Reject Ho at alpha = 0.01

Spring Final Exam Review

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