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.
Aspirin and Cardiovascular Disease. In the article by P. Ridker et al. titled “A Randomized Trial of Low-dose Aspirin in the Primary Prevention of Cardiovascular Disease in Women” (New England Journal of Medicine, Vol. 352, pp. 1293–1304), the researchers noted that “We randomly assigned 39,876 initially healthy women 45 years of age or older to receive 100 mg of aspirin or placebo on alternate days and then monitored them for 10 years for a first major cardiovascular
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- 1. To determine whether using a cell phone while driving increases the risk of an accident, a researcher examines accident reports to obtain data about the number of accidents in which a driver was talking on a cell phone. A. Is this a randomized experiment or an observational study? B. Assume that the accident reports show that people were more likely to have an accident while talking on a cell phone. Could this result be due to confounding?arrow_forwardExercise 6.28 provides data on sleep deprivation rates of Californians and Oregonians. The proportion of California residents who reported insucient rest or sleep during each of the preceding 30 days is 8.0%, while this proportion is 8.8% for Oregon residents. These data are based on simple random samples of 11,545 California and 4,691 Oregon residents. a) Conduct a hypothesis test to determine if these data provide strong evidence the rate of sleep deprivation is different for the two states. Use Oregon as Group A and California as Group B.Find the test statistic and p-value. b) It is possible the conclusion of the test in part (a) is incorrect. If this is the case, what type of error was made?arrow_forwardA U.S. Food Survey showed that Americans routinely eat beef in their diet. Suppose that in a study of 49 consumers in Illinois and 64 consumers in Texas the following results were obtained from two samples regarding average yearly beef consumption: Illinois Texas = 49 = 64 = 54.1lb = 60.4lb S1 = 7.0 S2 = 8.0 Formulate a hypothesis so that, if the null hypothesis is rejected, we can conclude that the average amount of beef eaten annually by consumers in Illinois is significantly less than that eaten by consumers in Texas.arrow_forward
- The following data are from a completely randomized design. Treatment A Treatment B Treatment C 32 44 33 30 43 36 30 44 35 26 46 36 32 48 40 Sample mean 30 45 36 Sample variance 6.00 4.00 6.50 At the level of significance, can we reject the null hypothesis that the means of the three treatments are equal? Use Fisher’s LSD procedure to test whether there is a significant difference between the means for treatments A and B, treatments A and C, and treatments B and C. Use . Use Fisher’s LSD procedure to develop a 95% confidence interval estimate of the difference between the means of treatments A and B.arrow_forwardThe following data represents results from an experiment comparing 3 treatment conditions for the cure of boredom. Treatment 1 is doing schoolwork, Treatment 2 is watching tv, and Treatment 3 is spending time with friends. The following scores represent treatment effectiveness scores where higher values indicate that the treatment of boredom was effective and lower values indicate that the treatment of boredom was ineffective. Treatment 1 Treatment 2 Treatment 3 0 1 6 N= 12 1 4 5 GM= 3.00 0 1 8 3 2 5…arrow_forwardFor large U.S. companies, what percentage of their total income comes from foreign sales? A random sample of technology companies (IBM, Hewlett-Packard, Intel, and others) gave the following information.† Technology companies, % foreign revenue: x1; n1 = 16 62.8 55.7 47.0 59.6 55.3 41.0 65.1 51.1 53.4 50.8 48.5 44.6 49.4 61.2 39.3 41.8 Another independent random sample of basic consumer product companies (Goodyear, Sarah Lee, H.J. Heinz, Toys 'R' Us) gave the following information. Basic consumer product companies,% foreign revenue: x2; n2 = 17 28.0 30.5 34.2 50.3 11.1 28.8 40.0 44.9 40.7 60.1 23.1 21.3 42.8 18.0 36.9 28.0 32.5 Assume that the distributions of percentage foreign revenue are mound-shaped and symmetric for these two company types. (a) Use a calculator with mean and standard deviation keys to calculate x1, s1, x2, and s2. (Round your answers to four decimal places.) x1 = % s1 = % x2 = % s2 = % (b) Let μ1 be the population mean…arrow_forward
- For large U.S. companies, what percentage of their total income comes from foreign sales? A random sample of technology companies (IBM, Hewlett-Packard, Intel, and others) gave the following information.† Technology companies, % foreign revenue: x1; n1 = 16 62.8 55.7 47.0 59.6 55.3 41.0 65.1 51.1 53.4 50.8 48.5 44.6 49.4 61.2 39.3 41.8 Another independent random sample of basic consumer product companies (Goodyear, Sarah Lee, H.J. Heinz, Toys 'R' Us) gave the following information. Basic consumer product companies,% foreign revenue: x2; n2 = 17 28.0 30.5 34.2 50.3 11.1 28.8 40.0 44.9 40.7 60.1 23.1 21.3 42.8 18.0 36.9 28.0 32.5 Assume that the distributions of percentage foreign revenue are mound-shaped and symmetric for these two company types. (a) Use a calculator with mean and standard deviation keys to calculate x1, s1, x2, and s2. (Round your answers to two decimal places.) x1 = % s1 = % x2 = % s2 = % (b) Let μ1 be the population mean for x1…arrow_forwardFor large U.S. companies, what percentage of their total income comes from foreign sales? A random sample of technology companies (IBM, Hewlett-Packard, Intel, and others) gave the following information. Technology companies, % foreign revenue: x1; n1 = 16 62.8 55.7 47.0 59.6 55.3 41.0 65.1 51.1 53.4 50.8 48.5 44.6 49.4 61.2 39.3 41.8 Another independent random sample of basic consumer product companies (Goodyear, Sarah Lee, H.J. Heinz, Toys 'R' Us) gave the following information. Basic consumer product companies,% foreign revenue: x2; n2 = 17 28.0 30.5 34.2 50.3 11.1 28.8 40.0 44.9 40.7 60.1 23.1 21.3 42.8 18.0 36.9 28.0 32.5 (Reference: Forbes Top Companies.) Assume that the distributions of percentage foreign revenue are mound-shaped and symmetric for these two company types. (a) Calculate x1, s1, x2, and s2. (Use 2 decimal places.) x1 % s1 % x2 % s2 % (b) Let ?1 be the population mean for x1 and let ?2 be the population…arrow_forwardFor large U.S. companies, what percentage of their total income comes from foreign sales? A random sample of technology companies (IBM, Hewlett-Packard, Intel, and others) gave the following information. Technology companies, % foreign revenue: x1; n1 = 16 62.8 55.7 47.0 59.6 55.3 41.0 65.1 51.1 53.4 50.8 48.5 44.6 49.4 61.2 39.3 41.8 Another independent random sample of basic consumer product companies (Goodyear, Sarah Lee, H.J. Heinz, Toys 'R' Us) gave the following information. Basic consumer product companies,% foreign revenue: x2; n2 = 17 28.0 30.5 34.2 50.3 11.1 28.8 40.0 44.9 40.7 60.1 23.1 21.3 42.8 18.0 36.9 28.0 32.5 Assume that the distributions of percentage foreign revenue are mound-shaped and symmetric for these two company types. (a) Use a calculator with mean and standard deviation keys to calculate x1, s1, x2, and s2. (Round your answers to four decimal places.) x1 = % s1 = % x2 = % s2 = % (b) Let ?1 be the population mean for x1…arrow_forward
- In Exercises 11 –14, test the claim about the difference between two population means u1 and u2 at the level of significance a. Assume the samples are random and independent, and the populations are normally distributed.arrow_forwardIn a study of the effectiveness of a new device that supports a weak or damaged heart, 150 people who consented to treatment were assigned at random to either a standard treatment consisting of drugs or the experimental treatment that consisted of drugs and surgery to install the new device. After two years, 60% of the 67 patients who received the device had improved and 40% of the patients who received the standard treatment had improved. Does this data provide convincing evidence that the proportion of patients who recieved the experimental treatment who improved is higher than for the patients who received the standard treatment? Test the relevant hypotheses using a significance level of 0.05. (Use pexperimental − pstandard ).A) State the null and alternative hypotheses. H0: pe − ps = 0, HA: pe − ps ≠ 0 H0: pe − ps = 0, HA: pe − ps < 0 H0: pe − ps = 0, HA: pe − ps > 0 B) Find the test statistic.z = C) What is the p-value?P-Value = D) State your conclusion in terms of…arrow_forwardA U.S. study published in The American Journal of Preventive Medicine compared state-level prevalence of firearm ownership in 2002 with state-level rates of firearm assault and firearm robbery in the subsequent year. The investigators found a positive association - meaning that states with higher prevalence of firearm ownership also tended to be the states with higher rates of firearm assault. Which design best describes this study? a)Observational cohort study b)Randomized trial c)Case-control study d)Ecological studyarrow_forward
- Holt Mcdougal Larson Pre-algebra: Student Edition...AlgebraISBN:9780547587776Author:HOLT MCDOUGALPublisher:HOLT MCDOUGAL