Concept explainers
Many people take ginkgo supplements advertised to improve memory. Are these over-the-counter supplements effective? In a study reported in the paper “Ginkgo for Memory Enhancement” (Journal of the American Medical Association [2002]: 835–840), elderly adults were assigned at random to either a treatment group or a control group. The 104 participants who were assigned to the treatment group took 40 mg of ginkgo three times a day for 6 weeks. The 115 participants assigned to the control group took a placebo pill three times a day for 6 weeks. At the end of 6 weeks, the Wechsler Memory Scale (a test of short-term memory) was administered. Higher scores indicate better memory
Based on these results, is there evidence that taking 40 mg of ginkgo three times a day is effective in increasing mean performance on the Wechsler Memory Scale? Test the relevant hypotheses using α = 0.05.
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Chapter 13 Solutions
Introduction to Statistics and Data Analysis
- What is meant by the sample space of an experiment?arrow_forwardWhat is an experiment?arrow_forwardKava is a beverage or extract that is made from Piper methysticum, a plant native to the western Pacific islands. Suppose that, in a randomized comparative experiment to determine if taking kava daily can reduce insomnia, a group of participants with insomnia were randomly assigned to take kava (treatment group) or a placebo (control group). After six weeks, the participants were interviewed to see if they experienced a decrease in insomnia. The table shows the results from the sample. The counts are the number of people in each group who experienced a decrease in insomnia. Group Description Population proportion Sample size Sample count Sample proportion 1 Treatment (kava) P1 n₁ = 402 x1 = 213 P₁ = 0.5299 2 Control (placebo) P2 n₂ = 521 x₂ = 121 P2 = 0.2322 Compute the standard error estimate, SE, of the difference in the sample proportions. Give your answer to at least four decimal places. 0.0438 SE = Incorrect Determine the value of the two-sample z-statistic for the difference in…arrow_forward
- An experiment was conducted for better understanding of the effectiveness of a particular type of drug for reducing bad cholesterol (LDL) level. The purpose of the experiment was to determine whether different dosages used have significant different outcomes in average LDL reduction. Twenty subjects with LDL at around 250 to 300 mg/dL had participated in the study and were randomly divided into four groups. Each group was given a specific level of dosage of the drug each day for one month, with a control group that only provided with placebo. The reduction in LDL was recorded and showed in the following table. Positive number indicates reduction and negative numbers indicates increasing in DLD. Use statistical software to analyze the data and answer the following question. Control Light Dosage Level Medium Dosage Level Heavy Dosage Level 7 25 73 81 -3 17 60 71 6 22 55 79 5 21 41 60 15 12 36 85 Perform a One-way…arrow_forwardResearchers recruited 1000 10- and 20-year-olds to participate in a study about age differences in aggression and the impact of violent video games on aggression. For 1-hour per day, half the participants were randomly assigned to play violent video games, while the other half played a nonviolent video game. A test for aggression was administered at the end of the year, and each participant received a score between 1 and 50 (higher scores indicate greater aggression). The results of the study are shown below: Factor 1 10 years 20 years old old Violent 35 25 Factor games 2 Nonviolent 25 45 games Is there a main effect of age? If so, which age shows more aggression?arrow_forwardIn a study, investigators surveyed individuals by telephone about how often they get tension headaches. One response variable that was measured was whether or not the respondent had experienced an episodic tension-type headache (ETTH) in the prior year. A headache pattern was called "episodic" if the headaches occurred less often than 15 times a month; otherwise, the headaches were called "chronic." Of the 1,660 women in the survey aged 18 to 29, a total of 658 said that they had experienced ETTHs in the last year. Of the 2,172 women in the 30- to 39-year-old age group, the number having experienced episodic headaches was 996. (a) Calculate the proportion who experienced an episodic headache in the prior year in the 18 to 29 group. (Round your answer to four decimal places.) Calculate the proportion who experienced an episodic headache in the prior year in the 30 to 39 group. (Round your answer to four decimal places.) Compute the difference in these two proportions. (Use p18…arrow_forward
- One study of cell phones and the risk of brain cancer looked at a group of 469 people who have brain cancer. The investigators then asked about the use of cell phones. Result: “Our data suggest that the use of hand- held cellular phones is not associated with risk of brain cancer. B . Based on this study, can you determine that cellular use does not CAUSE brain cancer? Why or why not?arrow_forwardIn a study of the adverse effects of x-rays among children, a retrospective cohort study was done using records from several large children's hospitals for the period of 1980 to 1985. 5,000 children were selected as a representative population of ill children seen at the hospitals during that time. Subjects were classified according to whether or not they received an x-ray during their stay in the hospital and were followed from their hospital stay through 2005 for the development of cancer. During the follow-up period, 30 incident cancers occurred in 3,000 children who had received an x-ray, and 5 incident cancers occurred in the 2,000 children who had not received an x-ray during their hospitalization. 1q. What are the rates of cancer incidence in each exposure group (per 1,000)? b.What is the attributable risk of cancer due to x-ray in this study population? 11c.. What is the risk ratio for the effect of exposure on the development of cancer in this study? What is the interpretation…arrow_forwardA colonoscopy is a medical procedure that is designed to find and remove precancerous lesions in the colon before they become cancerous. The article “Association of Colonoscopy and Death from Colorectal Cancer” reports that in a sample of 10,292 people diagnosed with colorectal cancer, 7.1% had previously had a colonoscopy. In a sample of 51,460 people without colorectal cancer, 9.8% had previously had a colonoscopy. 25. Can you conclude that the percentage of people who have had colonoscopies is greater in those without colorectal cancer? Use ? = 0.01arrow_forward
- Holt Mcdougal Larson Pre-algebra: Student Edition...AlgebraISBN:9780547587776Author:HOLT MCDOUGALPublisher:HOLT MCDOUGALCalculus For The Life SciencesCalculusISBN:9780321964038Author:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.Publisher:Pearson Addison Wesley,Glencoe Algebra 1, Student Edition, 9780079039897...AlgebraISBN:9780079039897Author:CarterPublisher:McGraw Hill
- College Algebra (MindTap Course List)AlgebraISBN:9781305652231Author:R. David Gustafson, Jeff HughesPublisher:Cengage Learning