Question: For a recent year, the fatality rate

> When randomly selecting a month, the probability of selecting a month with 32 or more days is 0.

> Find the probability of randomly selecting two different examinees and finding that they are both in Group A.

> When I toss four coins, there are four different possible outcomes that represent the event of one head and three tails.

> Does the idea of statistical significance apply to samples or populations? Briefly explain why.

> What do we mean when we say that a result is statistically significant?

> Suppose you toss a coin 100 times. Should you expect to get exactly 50 heads? Why or why not?

> A study was conducted to test the hypothesis that people can temporarily postpone death to survive a major holiday or important event such as a birthday. It was found that there were 6062 deaths in the week before Thanksgiving and 5938 in the week after

> New Jersey county clerks are supposed to use random selection to determine the order in which Democrat and Republican candidates are listed on an election ballot. Among the 41 selections listed on one county’s ballot, 40 of them showed the Democrat liste

> In a study of children injured in automobile crashes (published in American Journal of Public Health, Vol. 82, No. 3), those wearing seat belts had a mean stay of 0.83 day in an intensive care unit. Those not wearing seat belts had a mean stay of 1.39 da

> In a study by researchers at the University of Maryland, the body temperatures of 106 individuals were measured; the mean for the sample was 98.20F. It is commonly believed that the mean body temperature is 98.60F. The difference between the sample mea

> In a randomized controlled trial in Kenya, insecticide-treated Bed nets were tested as a way to reduce malaria. Among 343 infants who used the Bed nets, 15 developed malaria. Among 294 infants not using Bed nets, 27 developed malaria (based on data from

> The Genetics and IVF Institute conducted a clinical trial of its method for gender selection. The result showed that among 945 babies born to couples using the XSORT method of gender selection, 879 were girls. Is this result statistically significant?

> Find the probability of randomly selecting one of the examinees and getting someone who is in Group B or passed or both.

> An experiment was conducted to determine whether there is a difference in the success rates when carpal tunnel syndrome is treated with surgery or with splinting. The success rate for 73 patients treated with surgery was 92% and the success rate for 83 p

> Thirty identical cars are selected for a fuel test. Half of the cars are filled with regular gasoline, and the other half are filled with a new experimental fuel. The cars in the first group average 29.3 miles per gallon, while the cars in the second gro

> In a clinical trial of a new drug intended to treat allergies, 5 of the 80 subjects in the treatment group experienced headaches, and 8 of the 160 subjects in the control group experienced headaches.

> For a jury pool for one trial, 870 people were selected from a city population in which 79.1% are Americans of Mexican ancestry. Among the 870 selected people, 39% were Americans of Mexican ancestry.

> A commuter enters a New York City subway car near Times Square and finds that it is occupied by 50 men, all of whom are bald.

> Upon entering an aircraft that is nearly full, with 120 passengers, a traveler observes that nearly all of the passengers are adult females.

> In 10 rolls of a six-sided die, the outcome of 6 never occurs.

> In 10 rolls of a six-sided die, the outcome of 6 occurs every time.

> In preparation for a gubernatorial election in Florida, a pollster conducts a survey by randomly selecting 25 voters. He claims that the voters are randomly selected, but he finds that all of them are Independents.

> A student claims that he was not prepared for any of the ten true/false questions on a quiz, and he claims that all of his answers to those questions were random guesses. He finds that all ten of his answers were correct.

> If one of the examinees is randomly selected, find the probability of getting someone who passed the exam.

> In a clinical trial of a treatment for reducing back pain, the difference between the treatment group and the control group (which received no treatment) was found to be statistically significant. This means that the treatment will definitely ease back p

> In an experiment testing a method of gender selection intended to increase the likelihood that a baby is a girl, 1000 couples give birth to 501 girls and 499 boys. A company representative argues that this is evidence that the method is effective, becaus

> In an experiment testing a method of gender selection intended to increase the likelihood that a baby is a girl, 1000 couples give birth to 501 girls and 499 boys. An analyst argues that this fails to provide evidence that the method has any effect, beca

> Results from a study of heart disease have statistical significance because heart disease is such an important health risk for adults.

> What does it mean to say that a particular result is statistically significant at the 0.05 level or at the 0.01 level? Is a result that is statistically significant at the 0.05 level automatically also significant at the 0.01 level? What about the revers

> If one of the subjects is randomly selected, find the probability of selecting someone who told the truth or had a polygraph indication of telling the truth.

> If one of the subjects is randomly selected, find the probability of selecting someone who lied or had a polygraph indication of lying.

> If one of the subjects is randomly selected, find the probability of selecting someone who did not lie and had a polygraph indication of not lying.

> If one of the subjects is randomly selected, find the probability of selecting someone who lied.

> A study sponsored by AT&T and the Automobile Association of America included the sample data in the following table. a. Compare the percentage of cell phone users who had a crash to the percentage of people who did not use a cell phone and had a cras

> If P(A) = 0.65, what is the value of P(not A)?

> Using the samples of service times from all three restaurants, we obtain the analysis of variance results shown in Figure 10.7. Use a 0.05 significance level to test the claim that the three restaurants have the same mean service time.

> Using only the service times from McDonald’s, use a 0.05 significance level to test the claim that the sample is from a population with a mean of 180 seconds.

> Using only the service times from McDonald’s, construct a 95% confidence interval estimate of the population mean.

> A researcher collects paired sample data values and computes the value of the linear correlation coefficient to be 0. Based on that value, he concludes that there is no relationship between the two variables. What is wrong with this conclusion?

> In a study involving randomly selected subjects, it is found that there is a strong correlation between household income and number of visits to dentists. Is it valid to conclude that higher incomes cause people to visit dentists more often? Is it valid

> For 10 pairs of sample data values, the correlation coefficient is computed to be r = -1. What do you know about the scatterplot?

> Using the equation for the best-fit line, we find that when a slice of pizza costs $1000, the predicted subway fare is $1011. Is that predicted subway fare likely to be an accurate prediction? Why or why not?

> Does it appear that the best-fit line can be used to make a reasonably good prediction of subway fare given the cost of a slice of pizza?

> Find or estimate the value of r2. What does that value tell us?

> Can we conclude that the cost of a slice of pizza has a direct causal effect on the subway fare? Explain briefly.

> In a clinical trial of the effectiveness of a gender selection method, it is found that there is a 0.005 probability that the results could have occurred by chance. Does the method appear to be effective?

> Estimate the value of the correlation coefficient. What does that value suggest?

> Estimate the value of the linear correlation coefficient r for the points shown in the scatterplot in Figure 7.23.

> Construct a scatterplot. What does the result suggest?

> What is the meaning of small and large values of the test statistic F in ANOVA, and how do we use the value of F to decide whether to reject the null hypothesis at the 0.05 significance level?

> Describe and distinguish between the variance between samples and the variance within samples in ANOVA. How is the test statistic F related to the variance between samples and the variance within samples?

> Why is the method discussed in this section referred to as one-way analysis of variance? That is, what is “one-way” about the method?

> What does ANOVA stand for? What is the objective in using ANOVA? What form does the null hypothesis take?

> Listed below are measured amounts of greenhouse gas emissions from cars in three different categories. The measurements are in tons per year, expressed as CO2 equivalents. Use a 0.05 significance level to test the claim that the different car categories

> A student of one of the authors of this text lives in a home with a solar electric system. At the same time each day, she collected voltage readings (in volts) from a meter connected to the system and the results are listed in the accompanying table. Use

> The chest deceleration data (in g’s) from the tests described in Exercise 15 are given below. Use a 0.05 significance level to test the null hypothesis that the different size categories of cars have the same mean. Do the data suggest t

> In car crash experiments conducted by the National Transportation Safety Administration, new cars were purchased and crashed into a fixed barrier at 35 miles per hour. The subcompact cars were the Ford Escort, Honda Civic, Hyundai Accent, Nissan Sentra,

> The Binary Computer Company manufactures computer chips used in DVD players. The chips coming off the production line show a 27% yield, meaning that 27% of them are good and the others are defective. a. If one chip is randomly selected, find the probabil

> A random sample of adult females is partitioned into the age categories 18–24, 25–50, and over 50. The pulse rates of the subjects in the three different age categories are measured, and the analysis of variance result

> A random sample of M&Ms is partitioned into six categories according to color. The weights (in grams) are obtained, and the analysis of variance results are as shown in the display in Figure 10.5. a. What is the null hypothesis? b. What is the altern

> The Vertical Semirestrained Test was used to conduct flammability tests on children’s sleepwear. Pieces of fabric were burned under controlled conditions. After the burning stopped, the length of the charred portion was measured and rec

> Samples of Flesch-Kincaid Grade Level readability scores are obtained for randomly selected pages from books by Tom Clancy, J. K. Rowling, and Leo Tolstoy. The analysis of variance results from STATDISK are as shown in Figure 10.3. Assume that we want to

> A researcher obtains random samples of SAT scores from students at three different colleges. She plans to use the three sets of sample data with the method of analysis of variance. Identify the null and alternative hypotheses.

> Samples of airline departure times are obtained and compared to the scheduled departure times. Five major airlines are compared and their mean delay times are recorded. Identify the null and alternative hypotheses for applying an analysis of variance.

> An economist wants to compare the mean annual income of government employees in four different states. Analysis of variance cannot be used because there are more than three populations.

> The Atkins, Zone, Weight Watchers, and Ornish diets were tested in clinical trials. For each participant in the trials, the amount of weight loss was recorded, and results from analysis of variance show that the four diets are all effective in causing we

> In an ANOVA test for equality of mean IQ scores of students majoring in history, psychology, and art, the P-value of 0.242 is obtained. Based on the P-value, we cannot support the alternative hypothesis that at least one of the three means is different f

> In an ANOVA test for equality of mean skull breadths of Egyptian males from three different epochs, the P-value of 0.0031 is obtained. We conclude that the mean skull breadths from the three different epochs are all equal.

> Use subjective probability to estimate the probability of randomly selecting a car and selecting one that is black.

> Briefly explain the meaning of the  2 statistic. What does it tell us if the value of this statistic is small? How do you use the  2 statistic to decide whether to reject the null hypothesis?

> Explain what we mean by the observed frequency and expected frequency for each cell in a two-way table. What notation is used for the expected and observed frequencies? How do we calculate expected frequencies?

> What is a two-way table? What are the entries in its cells?

> The table below summarizes results from a survey of males aged 15 or older living in the Minhang District of China (based on data from “Cigarette Smoking in China” by Gong, Koplan, Feng, et al., Journal of the American

> The table below lists survey results obtained from a random sample of crime victims (based on data from the U.S. Department of Justice). Use a 0.01 significance level to test the claim that the type of crime is independent of whether the criminal was a s

> A random sample of 760 subjects was obtained, and each was tested for left-handed writing. Among the 240 males, 23 wrote with their left hand. Among the 520 females, 65 wrote with their left hand. The data are from the Education Resources Information Cen

> Of the 98 participants in a drug trial who were given a new experimental treatment for arthritis, 56 showed improvement. Of the 92 participants given a placebo, 49 showed improvement. Construct a two-way table for these data, and then use a 0.05 signific

> In a USA Today article about an experimental vaccine for children, the following statement appeared: “In a trial involving 1602 children, only 14 (1%) of the 1070 who received the vaccine developed the flu, compared with 95 (18%) of the

> Workers and senior-level bosses were asked if it was seriously unethical to monitor employee e-mails; the results are summarized in the following table (based on data from a Gallup poll). Use a 0.05 significance level to test the claim that the response

> In a study of high school students at least 16 years of age, researchers obtained the survey results summarized in the accompanying table (based on data from “Texting While Driving and Other Risky Motor Vehicle Behaviors Among U.S. High

> If three different subjects are randomly selected without replacement, find the probability that they all lied.

> The table below includes results from polygraph (lie detector) experiments conducted by researchers Charles R. Honts (Boise State University) and Gordon H. Barland (Department of Defense Polygraph Institute). In each case, it was known if the subject lie

> Test statistic:  2= 3.849; significance level: 0.01

> Test statistic:  2= 12.336; significance level: 0.01

> Test statistic:  2= 3.957; significance level: 0.05

> Test statistic:  2 = 3.499; significance level: 0.05

> Consider the following (hypothetical) data describing a survey in which dog and cat owners are asked whether they go for daily walks. Assume that we want to use a 0.01 significance level to test the claim that whether you own a dog or a cat is independen

> Consider the following data from a study of high school students at least 16 years of age (based on data from an article in Pediatrics). Assume that we want to use a 0.05 significance level to test the claim of independence between texting while driving

> The  2 statistic from my study was close to zero, so I rejected the null hypothesis.

> In a two-way table, all of the observed frequencies are lower than the expected frequencies, so the  2 statistic is negative.

> In a two-way table, all of the observed frequencies are very close to the expected frequencies, so the  2 statistics is very small.

> If two different subjects are randomly selected without replacement, find the probability that they both lied.

> In a two-way table for major and gender, the observed frequencies were very different from the expected frequencies, so I concluded that major and gender is independent variables.

> Briefly summarize the procedure for conducting a hypothesis test for a population mean when using the t distribution. What is the difference between the procedures using the normal and t distributions?

> Briefly summarize the procedure for constructing a 95% confidence interval around a sample mean when using the t distribution. What is the difference between the procedures using the normal and t distributions?

> How do you determine the number of degrees of freedom when using a t distribution? Once you know this number, how do you find the critical value of t that you will need for building a confidence interval or conducting a statistical test?

> What is the t distribution? What factors determine its shape? Describe conditions under which you could use a t distribution instead of a normal distribution when making inferences about a population mean.

> Use the sample data listed in Exercise 18 with a 0.05 significance level to test the claim that the sample is from a population with a mean less than 1.6 W/kg.

> Use the sample data listed in Exercise 17 with a 0.05 significance level to test the claim that the sample is from a population with a mean equal to 1000 cm3.

> The Carolina Tobacco Company advertised that its best-selling non filtered cigarettes contain 40 milligrams of nicotine or less, but Consumer Advocate magazine ran tests on 10 randomly selected cigarettes and found the amounts (in milligrams) shown below

> The National Highway Traffic Safety Administration conducted crash tests of child booster seats for cars. Listed below are results from those tests, with the measurements given in the standard unit “head injury condition” (hic). The safety requirement fo