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_forwardA particular paper described a study of children who were underweight or normal weight at age 2. Children in the sample were classified according to the number of sweet drinks consumed per day and whether or not the child was overweight one year after the study began. Is there evidence of an association between whether or not children are overweight after one year and the number of sweet drinks consumed? Assume that it is reasonable to regard the sample of children in this study as representative of 2 to 3 years old children and then test the appropriate hypotheses using a .05 significance level. (Round your answer to two decimal places.) Number of Sweet Overweight? Drinks Consumed per Day Yes No 22 930 1 73 2071 2 56 1681 3 or More 102 3389 x2 = | P-value interval Op< 0.001 O 0.001 s p < 0.01 O 0.01 sp < 0.05 O 0.05 sp < 0.10 Op2 0.10 There is --Select--- v to conclude that there is an association between whether or not children are overweight after one year and the number of sweet…arrow_forward
- Researchers 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_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_forwardAn 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_forward
- In 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_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_forwardOne 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_forward
- please help!!arrow_forwardA researcher is examining whether Omega-3 fish oil supplements improves memory functioning in patients with Alzheimer's Disease. The researcher recruits a random sample of 40 patients. Twenty patients are given an Omega-3 supplement every day for a month. The other twenty patients are given a placebo (AKA "sugar pill") every day for a month. After the month is over, all 40 participants complete a memory task. Scores on this task range from 1-20, with higher scores indicating better memory functioning. Use the data below to perform an independent groups t-test. Assume alpha = .05. Placebo Group: x-bar: 9.95 s-hat: 1.34 Omega-3 Group: x-bar: 11.70 s-hat: 0.98 S-hat pooled: 5.25 1) Is this an experimental or non-experimental study? Group of answer choices A)Experimental B) Non-Experimental 2) Is this a between- or within-subjects design? Group of answer choices A) Between-Subjects B) Within-Subjects 3) Write the null and alternative hypotheses: 4) Answer the following questions:…arrow_forwardImmunization of Schoolchildren. In the article, “Reasons for Non-uptake of Measles, Mumps, and Rubella Catch Up Immunisation in a Measles Epidemic and Side Effects of the Vaccine” (British Medical Journal, Vol. 310, pp. 1629–1632), R. Roberts et al. discussed a follow-up survey to examine why almost 10,000 children, ages 11–15, whose records showed no previous immunization were not immunized. In the survey, 10 of the 46 schools participating in the immunization campaign were randomly chosen and then the parents of all the nonimmunized children at the 10 selected schools were sent a questionnaire. What type of sampling design was used by these authors in their survey? Explain your answer.arrow_forward
- Holt Mcdougal Larson Pre-algebra: Student Edition...AlgebraISBN:9780547587776Author:HOLT MCDOUGALPublisher:HOLT MCDOUGALGlencoe Algebra 1, Student Edition, 9780079039897...AlgebraISBN:9780079039897Author:CarterPublisher:McGraw HillCollege Algebra (MindTap Course List)AlgebraISBN:9781305652231Author:R. David Gustafson, Jeff HughesPublisher:Cengage Learning