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A telephone poll of an SRS of 1234 adults found that 62% are generally satisfied with their lives. The announced margin of error for the poll was 3%. Does the margin of error account for the fact that some adults do not have telephones?

(e) No. The margin of error only includes sampling variability.

A significance test allows you to reject a null hypothesis H0 in favor of an alternative Ha at the 5% significance level. What can you say about significance at the 1% level?

(e) The answer can't be determined from the information given.

Which of the following statements about the sampling distribution of the sample mean is incorrect?

(e) The sampling distribution shows how the sample was distributed around the sample mean.

A random sample of 100 likely voters in a small city produced 59 voters in favor of Candidate A. The observed value of the test statistic for testing the null hypothesis H0: p = 0.5 versus the alternative hypothesis Ha: p > 0.5 is

(b) z = 0.59-0.5/(sr0.5(0.5)/100)

Suppose we select an SRS of size n = 100 from a large population having proportion P of successes. Let P be the proportion of successes in the sample. For which value of p would it be safe to use the Normal approximation to the sampling distribution of P hat?

(c) 0.85

The expected count of cases with lymphoma in homes with an HCC is

(a) 79 x 31/215

The Gallup Poll interviews 1600 people. Of these, 18% say that they jog regularly. The news report adds: "The poll had a margin of error of plus or minus three percentage points at a 95% confidence level." You can safely conclude that

(a) 95% of all Gallup Poll samples like this one give answers within ± 3% of the true population value.

The power takeoff driveline on tractors used in agriculture is a potentially serious hazard to operators of farm equipment. The driveline is covered by a shield in new tractors, but for a variety of reasons, the shield is often missing on older tractors. Two types of shields are the bolt-on and the flip-up. It was believed that the bolt-on shield was perceived as a nuisance by the operators and deliberately removed, but the flip-up shield is easily lifted for inspection and maintenance and may be left in place. In a study initiated by the U.S. National Safety Council, random samples of older tractors with both types of shields were taken to see what proportion of shields were removed. Of 183 tractors designed to have bolt-on shields, 35 had been removed. Of the 136 tractors with flip-up shields, 15 were removed. We wish to perform a test of H0: pb = pf versus Ha: pb > pf, where pb and pf are the proportions of all tractors with the bolt-on and flip-up shields removed, respectively. Which of the following is not a condition for performing the significance test?

(a) Both populations are Normally distributed.

A radio talk show host with a large audience is interested in the proportion p of adults in his listening area who think the drinking age should be lowered to eighteen. To find this out, he poses the following question to his listeners: "Do you think that the drinking age should be reduced to eighteen in light of the fact that eighteen-year-olds are eligible for military service?" He asks listeners to phone in and vote "Yes" if they agree the drinking age should be lowered and "No" if not. Of the 100 people who phoned in, 70 answered "Yes." Which of the following conditions for inference about a proportion using a confidence interval are violated? I. The data are a random sample from the population of interest. II. The population is at least 10 times as large as the sample. III. n is so large that both n and n(1 − ) are at least 10.

(a) I only

An SRS of 100 postal employees found that the average time these employees had worked at the postal service was 7 years with standard deviation 2 years. Do these data provide convincing evidence that the mean time of employment μ for the population of postal employees has changed from the value of 7.5 that was true 20 years ago? To determine this, we test the hypotheses H0: μ = 7.5 versus Ha: μ ≠ 7.5 using a one-sample t test. What conclusion should we draw at the 5% significance level?

(a) There is convincing evidence that the mean time working with the postal service has changed

A quiz question gives random samples of n = 10 observations from each of two Normally distributed populations. Tom uses a table of t distribution critical values and 9 degrees of freedom to calculate a 95% confidence interval for the difference in the two population means. Janelle uses her calculator's two-sample t interval with 16.87 degrees of freedom to compute the 95% confidence interval. Assume that both students calculate the intervals correctly. Which of the following is true?

(a) Tom's confidence interval is wider.

The central limit theorem is important in statistics because it allows us to use the Normal distribution to find probabilities involving the sample mean

(a) if the sample size is reasonably large (for any population).

Researchers are interested in evaluating the effect of a natural product on reducing blood pressure. This will be done by comparing the mean reduction in blood pressure of a treatment (natural product) group and a placebo group using a two-sample t test. The researchers would like to be able to detect whether the natural product reduces blood pressure by at least 7 points more, on average, than the placebo. If groups of size 50 are used in the experiment, a two-sample t test using α = 0.01 will have a power of 80% to detect a 7-point difference in mean blood pressure reduction. If the researchers want to be able to detect a 5-point difference instead, then the power of the test

(a) would be less than 80%.

Thirty-five people from a random sample of 125 workers from Company A admitted to using sick leave when they weren't really ill. Seventeen employees from a random sample of 68 workers from Company B admitted that they had used sick leave when they weren't ill. A 95% confidence interval for the difference in the proportions of workers at the two companies who would admit to using sick leave when they weren't ill is

(b)

Seventeen people have been exposed to a particular disease. Each one independently has a 40% chance of contracting the disease. A hospital has the capacity to handle 10 cases of the disease. What is the probability that the hospital's capacity will be exceeded?

(b) 0.035

What is the probability that a randomly chosen subject completes more than the expected number of puzzles in the five-minute period while listening to soothing music?

(b) 0.4

You want to compute a 90% confidence interval for the mean of a population with unknown population standard deviation. The sample size is 30. The value of t* you would use for this interval is

(b) 1.699.

A researcher initially plans to take an SRS of size n from a population that has mean 80 and standard deviation 20. If he were to double his sample size (to 2n), the standard deviation of the sampling distribution of the sample mean would be multiplied by

(b) 1/sr2

A test for extrasensory perception (ESP) involves asking a person to tell which of 5 shapes—a circle, star, triangle, diamond, or heart—appears on a hidden computer screen. On each trial, the computer is equally likely to select any of the 5 shapes. Suppose researchers are testing a person who does not have ESP and so is just guessing on each trial. What is the probability that the person guesses the first 4 shapes incorrectly but gets the fifth correct?

(c) (4/5)^4 x (1/5)

All current-carrying wires produce electromagnetic (EM) radiation, including the electrical wiring running into, through, and out of our homes. High-frequency EM radiation is thought to be a cause of cancer. The lower frequencies associated with household current are generally assumed to be harmless. To investigate the relationship between current configuration and type of cancer, researchers visited the addresses of a random sample of children who had died of some form of cancer (leukemia, lymphoma, or some other type) and classified the wiring configuration outside the dwelling as either a high-current configuration (HCC) or a low-current configuration (LCC). Here are the data: Computer software was used to analyze the data. The output included the value χ2 = 0.435. T11.7. The appropriate degrees of freedom for the χ2 statistic is

(b) 2.

A chi-square test is used to test whether a 0 to 9 spinner is "fair" (that is, the outcomes are all equally likely). The spinner is spun 100 times, and the results are recorded. The degrees of freedom for the test will be

(b) 9.

The figure shows the probability distribution of a discrete random variable X. Note that the cursor is on the histogram bar representing a value of 6. Which of the following best describes this random variable?

(b) Binomial with n = 8, p = 0.3

An opinion poll asks a random sample of adults whether they favor banning ownership of handguns by private citizens. A commentator believes that more than half of all adults favor such a ban. The null and alternative hypotheses you would use to test this claim are

(b) H0: p = 0.5; Ha: p > 0.5

The weight of tomatoes chosen at random from a bin at the farmer's market follows a Normal distribution with mean μ = 10 ounces and standard deviation σ = 1 ounce. Suppose we pick four tomatoes at random from the bin and find their total weight T. The random variable T is

(b) Normal, with mean 40 ounces and standard deviation 2 ounces.

The number of undergraduates at Johns Hopkins University is approximately 2000, while the number at Ohio State University is approximately 60,000. At both schools, a simple random sample of about 3% of the undergraduates is taken. Each sample is used to estimate the proportion p of all students at that university who own an iPod. Suppose that, in fact, p = 0.80 at both schools. Which of the following is the best conclusion?

(b) The estimate from Johns Hopkins has more sampling variability than that from Ohio State.

The student newspaper at a large university asks an SRS of 250 undergraduates, "Do you favor eliminating the carnival from the term-end celebration?" All in all, 150 of the 250 are in favor. Suppose that (unknown to you) 55% of all undergraduates favor eliminating the carnival. If you took a very large number of SRSs of size n = 250 from this population, the sampling distribution of the sample proportion P would be

(b) approximately Normal with mean 0.55 and standard deviation 0.03.

How much more effective is exercise and drug treatment than drug treatment alone at reducing the rate of heart attacks among men aged 65 and older? To find out, researchers perform a completely randomized experiment involving 1000 healthy males in this age group. Half of the subjects are assigned to receive drug treatment only, while the other half are assigned to exercise regularly and to receive drug treatment. The most appropriate inference method for answering the original research question is

(b) two-sample z interval for p1 − p2.

A machine is designed to fill 16-ounce bottles of shampoo. When the machine is working properly, the amount poured into the bottles follows a Normal distribution with mean 16.05 ounces and standard deviation 0.1 ounce. Assume that the machine is working properly. If four bottles are randomly selected and the number of ounces in each bottle is measured, then there is about a 95% chance that the sample mean will fall in which of the following intervals?

(c) 15.95 to 16.15 ounces

To determine the reliability of experts who interpret lie detector tests in criminal investigations, a random sample of 280 such cases was studied. The results were *pic of table* If the hypotheses are H0: suspect is innocent versus Ha: suspect is guilty, then we could estimate the probability that experts who interpret lie detector tests will make a Type II error as

(c) 15/140.

A study of voting chose 663 registered voters at random shortly after an election. Of these, 72% said they had voted in the election. Election records show that only 56% of registered voters voted in the election. Which of the following statements is true about the boldface numbers?

(c) 72% is a statistic and 56% is a parameter.

A 90% confidence interval for the mean μ of a population is computed from a random sample and is found to be 9 ± 3. Which of the following could be the 95% confidence interval based on the same data?

(c) 9 ± 4

In preparing to construct a one-sample t interval for a population mean, suppose we are not sure if the population distribution is Normal. In which of the following circumstances would we not be safe constructing the interval based on an SRS of size 24 from the population?

(c) A boxplot of the data has a large outlier.

At a baseball game, 42 of 65 randomly selected people own an iPod. At a rock concert occurring at the same time across town, 34 of 52 randomly selected people own an iPod. A researcher wants to test the claim that the proportion of iPod owners at the two venues is different. A 90% confidence interval for the difference in population proportions (game − concert) is (− 0.154, 0.138). Which of the following gives the correct outcome of the researcher's test of the claim?

(c) Because the confidence interval includes 0, the researcher cannot conclude that the proportion of iPod owners at the two venues is different.

The category that contributes the largest component to the χ2 statistic is

(c) Hispanic.

Recent revenue shortfalls in a midwestern state led to a reduction in the state budget for higher education. To offset the reduction, the largest state university proposed a 25% tuition increase. It was determined that such an increase was needed simply to compensate for the lost support from the state. Separate random samples of 50 freshmen, 50 sophomores, 50 juniors, and 50 seniors from the university were asked whether they were strongly opposed to the increase, given that it was the minimum increase necessary to maintain the university's budget at current levels. Here are the results. *insert table* T11.2. Which hypotheses would be appropriate for performing a chi-square test?

(c) The null hypothesis is that the distribution of student opinion about the proposed tuition increase is the same for each of the 4 years at this university. The alternative is that the distribution is different for at least 2 of the 4 years.

Which of the following random variables is geometric?

(c) The number of digits I read in a randomly selected row of the random digits table until I find a 7.

Are TV commercials louder than their surrounding programs? To find out, researchers collected data on 50 randomly selected commercials in a given week. With the television's volume at a fixed setting, they measured the maximum loudness of each commercial and the maximum loudness in the first 30 seconds of regular programming that followed. Assuming conditions for inference are met, the most appropriate method for answering the question of interest is

(c) a paired t test.

We compute the value of the χ2 statistic to be 6.58. Assuming that the conditions for inference are met, the P-value of our test is

(c) between 0.05 and 0.10.

An SRS of size 100 is taken from Population A with proportion 0.8 of successes. An independent SRS of size 400 is taken from Population B with proportion 0.5 of successes. The sampling distribution for the difference (Population A-Population B) in sample proportions has what mean and standard deviation?

(c) mean = 0.3; standard deviation = 0.047

The Gallup Poll has decided to increase the size of its random sample of voters from about 1500 people to about 4000 people right before an election. The poll is designed to estimate the proportion of voters who favor a new law banning smoking in public buildings. The effect of this increase is to

(c) reduce the variability of the estimate.

A researcher claims to have found a drug that causes people to grow taller. The coach of the basketball team at Brandon University has expressed interest but demands evidence. Over 1000 Brandon students volunteer to participate in an experiment to test this new drug. Fifty of the volunteers are randomly selected, their heights are measured, and they are given the drug. Two weeks later, their heights are measured again. The power of the test to detect an average increase in height of 1 inch could be increased by

(c) using α = 0.05 instead of α = 0.01.

In a test of H0: p = 0.4 against Ha : p ≠ 0.4, a random sample of size 100 yields a test statistic of z = 1.28. The P-value of the test is approximately equal to

(d) 0.20.

Let D be the difference in the number of puzzles solved by two randomly selected subjects in a five-minute period. What is the standard deviation of D?

(d) 1.27

A random sample of traffic tickets given to motorists in a large city is examined. The tickets are classified according to the race of the driver. The results are summarized in the following table. The proportion of this city's population in each of the racial categories listed above is as follows: We wish to test H0: The racial distribution of traffic tickets in the city is the same as the racial distribution of the city's population. T11.4. Assuming H0 is true, the expected number of Hispanic drivers who would receive a ticket is

(d) 11.84.

The weights (in pounds) of three adult males are 160, 215, and 195. The standard error of the mean of these three weights is

(d) 16.07.

Suppose we want a 90% confidence interval for the average amount spent on books by freshmen in their first year at a major university. The interval is to have a margin of error of $2. Based on last year's book sales, we estimate that the standard deviation of the amount spent will be close to $30. The number of observations required is closest to

(d) 609.

Many television viewers express doubts about the validity of certain commercials. In an attempt to answer their critics, Timex Group USA wishes to estimate the proportion of consumers who believe what is shown in Timex television commercials. Let p represent the true proportion of consumers who believe what is shown in Timex television commercials. What is the smallest number of consumers that Timex can survey to guarantee a margin of error of 0.05 or less at a 99% confidence level?

(d) 700

The standard deviation of X is 0.9. Which of the following is the best interpretation of this value?

(d) The number of puzzles solved by subjects typically differed from the mean by about 0.9 puzzles.

Which of the following may we conclude, based on the test results?

(d) There is not convincing evidence of an association between wiring configuration and the type of cancer that caused the deaths of children in the study.

A Census Bureau report on the income of Americans says that with 90% confidence the median income of all U.S. households in a recent year was $57,005 with a margin of error of ±$742. This means that

(d) the Census Bureau got the result $57,005 ± $742 using a method that will capture the true median income 90% of the time when used repeatedly.

A Type I error would occur if we found convincing evidence that

(d) there is an association between the type of wiring and the form of cancer when there actually is no association.

A certain vending machine offers 20-ounce bottles of soda for $1.50. The number of bottles X bought from the machine on any day is a random variable with mean 50 and standard deviation 15. Let the random variable Y equal the total revenue from this machine on a given day. Assume that the machine works properly and that no sodas are stolen from the machine. What are the mean and standard deviation of Y?

(d) μY = $75, σY = $22.50

A researcher wished to compare the average amount of time spent in extracurricular activities by high school students in a suburban school district with that in a school district of a large city. The researcher obtained an SRS of 60 high school students in a large suburban school district and found the mean time spent in extracurricular activities per week to be 6 hours with a standard deviation of 3 hours. The researcher also obtained an independent SRS of 40 high school students in a large city school district and found the mean time spent in extracurricular activities per week to be 5 hours with a standard deviation of 2 hours. Suppose that the researcher decides to carry out a significance test of H0: μsuburban = μcity versus a two-sided alternative. T10.5. The correct test statistic is

(e)

The conditions for carrying out the chi-square test in exercise T11.2 are I. Independent random samples from the populations of interest. II. All expected counts are at least 5. III. The population sizes are at least 10 times the sample sizes. Which of the conditions is (are) satisfied in this case?

(e) I, II, and III

A 95% confidence interval for a population mean μ is calculated to be (1.7, 3.5). Assume that the conditions for performing inference are met. What conclusion can we draw for a test of H0: μ = 2 versus Ha: μ ≠ 2 at the α = 0.05 level based on the confidence interval?

(e) We would fail to reject H0 at level α = 0.05.

Suppose a student is randomly selected from your school. Which of the following pairs of random variables are most likely independent?

(e) X = average amount of homework the student does per night; Y = student's height

A study of road rage asked separate random samples of 596 men and 523 women about their behavior while driving. Based on their answers, each respondent was assigned a road rage score on a scale of 0 to 20. Are the conditions for performing a two-sample t test satisfied?

(e) Yes; we have two independent random samples and large sample sizes.

You are thinking of conducting a one-sample t test about a population mean μ using a 0.05 significance level. Which of the following statements is correct?

(e) You can safely carry out the test if your sample size is at least 30.

The P-value for the test is 0.048. A correct conclusion is to

(e) reject H0 at the α = 0.05 level. There is convincing evidence of a difference in the average time spent on extracurricular activities by students in the suburban and city school districts.

Suppose that you are a student aide in the library and agree to be paid according to the "random pay" system. Each week, the librarian flips a coin. If the coin comes up heads, your pay for the week is $80. If it comes up tails, your pay for the week is $40. You work for the library for 100 weeks. Suppose we choose an SRS of 2 weeks and calculate your average earnings . The shape of the sampling distribution of x will be

(e) symmetric but not Normal.