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.
1.17 The Salk Vaccine. In the 1940s and early 1950s, the public was greatly concerned about polio. In an attempt to prevent this disease, Jonas Salk of the University of Pittsburgh developed a polio vaccine. In a test of the vaccine’s efficacy, involving nearly 2 million grade-school children, half of the children received the Salk vaccine; the other half received a placebo, in this case an injection of salt dissolved in water. Neither the children nor the doctors performing the diagnoses knew which children belonged to which group, but an evaluation center did. The center found that the incidence of polio was far less among the children inoculated with the Salk vaccine. From that information, the researchers concluded that the vaccine would be effective in preventing polio for all U.S. school children; consequently, it was made available for general use.
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Introductory Statistics (10th Edition)
- 1 (part 2). Does When Food Is Eaten Affect Weight Gain?A study was introduced that examined the effect of light at night on weight gain in mice. In the full study of 27 mice over a four-week period, the mice who had a light on at night gained significantly more weight than the mice with darkness at night, despite eating the same number of calories and exercising the same amount. Researchers noticed that the mice with light at night ate a greater percentage of their calories during the day (when mice are supposed to be sleeping). The computer output shown below allows us to examine the relationship between percent of calories eaten during the day, DayPct, and body mass gain in grams, BMGain. A scatterplot with regression line is also shown below (attached image).Pearson correlation of BMGain and DayPct =0.740P-Value =0.000--------------------------------------------------------------The regression equation isBMGain=1.11+0.127DayPct Predictor Coef SE Coef T P Constant 1.113 1.382…arrow_forwardIn a study of exhaust emissions from school buses, the pollution intake by passengers was determined for a sample of nine school buses used in the Southern California Air Basin. The pollution intake is the amount of exhaust emissions, in grams per person per million grams emitted, that would be inhaled while traveling on the bus during its usual 18-mile18-mile trip on congested freeways from South Central LA to a magnet school in West LA. (In comparison, a city of 11 million people will inhale a total of about 1212 grams of exhaust per million grams emitted.) The amounts for the nine buses when driven with the windows open are given in the table. 1.15 0.33 0.40 0.33 1.35 0.38 0.25 0.40 0.35 A good way to judge the effect of outliers is to do your analysis twice, once with the outliers and a second time without them. Give the 90%90% confidence interval with all the data for the mean pollution intake among all school buses used in the Southern California Air Basin that…arrow_forward4.16: what was the effect of the experimental course?arrow_forward
- A test of body reaction to the Malaysian citizens who have taken their vaccine was conducted. Selected citizens who got side effect are categorised according to their blood type and the type of vaccine received. From a sample of 250 citizens, 150 of them were administered with Sinovac while the rest received AstraZeneca. Table 4 shows the number of citizens who had side effect after being vaccinated. Type of vaccine Blood type A B AB O Sinovac 50 M 50 20 AstraZeneca 30 20 20 N Does different blood type among people who had side effect relate to the type of vaccinereceived at A=0.025?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_forwardIn the book Business Research Methods (5th ed.), Donald R. Cooper and C. William Emory discuss studying the relationship between on-the-job accidents and smoking. Cooper and Emory describe the study as follows: Suppose a manager implementing a smoke-free workplace policy is interested in whether smoking affects worker accidents. Since the company has complete reports of on-the-job accidents, she draws a sample of names of workers who were involved in accidents during the last year. A similar sample from among workers who had no reported accidents in the last year is drawn. She interviews members of both groups to determine if they are smokers or not. The sample results are given in the following table. On-the-Job Accident Smoker Yes No Row Total Heavy 12 5 17 Moderate 9 10 19 Nonsmoker 13 17 30 Column total 34 32 66 Expected counts are below observed counts Accident No Accident Total Heavy 12 5 17 8.76 8.24…arrow_forward
- The 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_forward6. In the book Business Research Methods (5th ed.), Donald R. Cooper and C. William Emory discuss studying the relationship between on-the-job accidents and smoking. Cooper and Emory describe the study as follows: Suppose a manager implementing a smoke-free workplace policy is interested in whether smoking affects worker accidents. Since the company has complete reports of on-the-job accidents, she draws a sample of names of workers who were involved in accidents during the last year. A similar sample from among workers who had no reported accidents in the last year is drawn. She interviews members of both groups to determine if they are smokers or not. The sample results are given in the following table.arrow_forward
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