In Exercises 1.17–1.22, state whether the investigation in question is an observational study or a designed experiment. Justify your answer in each case.
Heart Failure. In the paper “Cardiac-Resynchronization Therapy with or without an Implantable Defibrillator in Advanced Chronic Heart Failure” (New England Journal of Medicine, Vol. 350, pp. 2140–2150), M. Bristow et al. reported the results of a study of methods for treating patients who had advanced heart failure due to ischemic or nonischemic cardiomyopathies. A total of 1520 patients were randomly assigned in a 1:2:2 ratio to receive optimal pharmacologic therapy alone or in combination with either a pacemaker or a pacemaker–defibrillator combination. The patients were then observed until they died or were hospitalized for any cause.
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Introductory Statistics (10th Edition)
- section9.2 42a. True or false: If P = 0.08, then a. The result is statistically significant at the α = 0.05 level.arrow_forwardWelsh, Davis, Burke, and Williams (2002) conducted a study to evaluate the effectiveness of a carbohydrate-electrolyte drink on sports performance and endurance. Experienced athletes were given either a carbohydrate-electrolyte drink or a placebo while they were tested on a series of high-intensity exercises. One measure was how much time it took for the athletes to run to fatigue. Data similar to the results obtained in the study are shown in the following table. Time to Run to Fatigue (in minutes) Mean SE Placebo 21.7 2.2 Carbohydrate- electrolyte 28.6 2.7 a) Construct a bar graph that incorporates all of the information in the table. b) Looking at your graph, do you think that the carbohydrate-electrolyte drink helps performance?arrow_forwardThe Great White Shark. In an article titled “Great White, Deep Trouble” (National Geographic, Vol. 197(4), pp. 2–29), Peter Benchley—the author of JAWS—discussed various aspects of the Great White Shark (Carcharodon carcharias). Data on the number of pups borne in a lifetime by each of 80 Great White Shark females are provided on the WeissStats site. Use the technology of your choice to a. obtain frequency and relative-frequency distributions, using single-value grouping. b. construct and interpret either a frequency histogram or a relativefrequency histogram.arrow_forward
- I. The development of viral hepatitis subsequent to a blood transfusion can cause serious complications for a patient. The article, "Hepatitis in Patients with Acute Nonlymphatic Leukemia" (Amer. J. of Med. (1983): 413-421) reported that in spite of careful screening for those having a hepatitis antigen, viral hepatitis occurs in 7% of blood recipients. Suppose a new treatment is believed to reduce the incidence of viral hepatitis. The treatment is given to 200 blood recipients and only 6 contract hepatitis. Does it appear that the treatment is'effective? That is, is it very likely that we would observe only 6/200 contract hepatitis when 7% of the population is known to do so?arrow_forwardThe Lion’sMane. In a study by P. M.West titled “The Lion’s Mane” (American Scientist, Vol. 93, No. 3, pp. 226–236), the effects of the mane of a male lion as a signal of quality to mates and rivals was explored. Four life-sized dummies of male lions provided a tool for testing female response to the unfamiliar lions whose manes varied by length (long or short) and color (blonde or dark). The female lions were observed to see whether they approached each of the four life-sized dummies. a. experimental units. b. response variable. c. factor(s). d. levels of each factor. e. treatments.arrow_forwardThe article “The Effect of Restricting Opening Hours on Alcohol-Related Violence” (S. Duailibi, W. Ponicki, et al., American Journal of Public Health, 2007:2276–2280) presented homicide rates for the years 1995–2005 for the town of Diadema, Brazil. In 2002, a law was passed requiring bars to close at 11 pm each night. After the law's passage, the homicide rate dropped by an average of 9 homicides per month, a statistically significant decrease. Which of the following is the best conclusion? a) It is reasonable to conclude that the law is responsible for a reduction of 9 homicides per month. b) It is reasonable to conclude that the law is responsible for a reduction in homicides, but the actual amount might be somewhat more or less than 9 per month. c) It is reasonable to conclude that the homicide rate decreased, but the law may not have anything to do with the decrease. d) It is plausible that the homicide rate may not have decreased at all after the passage of the law.arrow_forward
- Welsch, Davis, Burke, and Williams (2002) conducted a study to evaluate the effectiveness of a carbohydrate-electrolyte drink on sports performance and endurance. Experienced athletes were given either a carbohydrate-electrolyte drink or a placebo while they were tested on a series of high-intensity exercises. One measure was how much time it took for the athletes to run to fatigue. Data similar to the results obtained in the study are shown in the following table: 8.3 Time to run to fatigue (in minutes) Group Mean SE (standard error) Placebo 21.7 2.2 Carbohydrate-electrolyte 28.6 2.7 Construct a bar graph that incorporates all of the information in the table. Looking at your graph, do you think that the carbohydrate-electrolyte drink helps performance? а. b.arrow_forwardWhat determines how much money a family spends on holiday? In a survey, a sample of 30 families were asked to keep a record of their spending during a one-week holiday and report their total spending at the end of the week. The researchers hypothesised that wealthier families tend to spend more, and that families who tend to spend most of the time in one town tend to spend less than those who travel around to see sight at several different places. Therefore, the respondents were asked to report the net monthly income of the family as well as the number of different settlements (villages, towns, and cities) that they visited during the week. A multiple linear regression model revealed that both income and the amount of travelling are significantly related to total spending. The researchers, however, also hypothesised that the two independent variables may interact. The printout below shows the SPSS output for fitting an interaction model to the data. < Model 1 Model 1 R .866ª Model 1…arrow_forwardEight people with high blood cholesterol have changed their diets to avoid foods high in cholesterol, such as meats and dairy products. After two months on this diet, their cholesterol levels are re-measured. The following data are changes in their cholesterol levels in mg/dL (=final measure –initial measure): -40 -27 14 -8 -31 10 -38 -26 a. Test the hypothesis that consuming a low cholesterol diet for two months affects blood cholesterol levels. (Hint: if there is a difference, then the change won’t be equal to zero.) Follow the 4 steps of hypothesis testing, stating your null and alternative hypothesis in symbols, and giving a complete finding in plain English with detailed statistical notation. b. Now test the hypothesis that consuming a low cholesterol diet for two months decreases blood cholesterol levels by 10 mg/dL. Again, show all 4 steps. (Hint: remember that a null hypothesis of “no…arrow_forward
- Demarion Santana is interested in studying the growth rates of capsicum annuum (pepper) plants under bridges in California. He randomly selects 50 bridges in California and records the frequency, height, and number of peppers on any plants growing under these bridges. His results were published in the Almanac of Questionable Statistics, Vol 1 (2016). What is the population in this study? Question 12 options: 1) All capsicum annuum plants growing under bridges in California 2) All capsicum annuum plants growing anywhere in California 3) Capsicum annuum plants growing under the 50 bridges randomly selected to be included in the study 4) Readers of the Almanac of Questionable Statisticsarrow_forwardThe authors of the paper "Statistical Methods for Assessing Agreement Between Two Methods of Clinical Measurement" compared two different instruments for measuring a subject's ability to breathe out air.+ (This measurement is helpful in diagnosing various lung disorders.) The two instruments considered were a Wright peak flow meter and a mini-Wright peak flow meter. Seventeen subjects participated in the study, and for each subject air flow was measured once using the Wright meter and once using the mini-Wright meter. Mini- Subject Wright Meter 1 2 3 4 5 6 7 8 9 512 430 520 428 500 600 364 380 658 Wright Meter 494 395 516 434 476 557 413 442 650 Subject 10 11 12 13 14 15 16 17 Mini- Wright Meter 445 432 626 260 477 259 350 451 Wright Meter 433 417 656 267 478 178 423 427 (a) Suppose that the Wright meter is considered to provide a better measure of air flow, but the mini-Wright meter is easier to transport and to use. If the two types of meters produce different readings but there is a…arrow_forwardIron is an integral part of many proteins and enzymes that maintain good health. Recommendations for iron were developed by an institute of medicine for a certain region. The recommended dietary allowance (RDA) of iron for adult females under the age of 51 years is 17.5 milligrams (mg) per day. A hypothesis test is to be performed to decide whether adult females under the age of 51 years are, on average, getting more than the RDA of 17.5 mg of iron per day. Complete parts (a) through (c). a. Determine the null hypothesis. Ho: H mg (Type an integer or a decimal. Do not round.)arrow_forward
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