Concept explainers
The effectiveness of antidepressants in treating the eating disorder bulimia was examined in the article “Bulimia Treated with Imipramine: A Placebo-Controlled Double-Blind Study” (American Journal of Psychology [1983]: 554–558). A group of patients diagnosed with bulimia were randomly assigned to one of two treatment groups, one receiving imipramine and the other a placebo. One of the variables recorded was binge frequency. The authors chose to analyze the data using a rank-sum test because it makes no assumption of normality. They stated that “because of the wide
Data on number of binges during one week that are consistent with the findings of the article are given in the following table:
Do these data strongly suggest that imipramine is effective in reducing the
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INTRODUCTION TO STATISTICS & DATA ANALYS
- A study was performed on 200 elementary school students to investigate whether regular Vitamin A supplementation was effective in preventing colds during the month of March. 100 were randomized to receive daily Vitamin A supplements during the month of March, and 100 students were randomized to a placebo group (and did not receive Vitamin A) during the same month. The number of students getting at least one cold in March was computed in the two groups, and the results are given in the following 2 X 2 table. Using a 5% level of significance determine whether there is an association between Vitamin A supplementation and prevention of Common Cold ColdNo Cold Vitamin A1585100 Placebo2575100 40160200arrow_forwardA cross-sectional study is conducted to investigate cardiovascular disease (CVD) risk factors among a sample of patients seeking medical care at one of three local hospitals. A total of 500500 patients are enrolled. Based on the following data, we would like to determine if there is a significant association between the family history of CVD and the enrollment site. Enrollment Site Family History of CVD Hospital 1 Hospital 2 Hospital 3 Total Yes 34 8 58 100 No 104 72 224 400 Total 138 80 282 500 Given: The value of the test statistic is χ2= 6.912 Use α=0.1 as the level of significance. The superintendent of Hospital 2 performed the Goodness of Fit Test to test whether 25% of the patients go to Hospital 1, 15% of the patients go to Hospital 2 and 60% of the patients go to Hospital 3. Given: The superintendent found that the pp-value for the test is 0.25091 Let: p1=p1= be the proportion of patients at Hospital 1 p2=p2= be the proportion of patients at…arrow_forwardIn its January 25, 2012, issue, the Journal of the American Medical Association reported on the effects of overconsumption of low, normal, and high protein diets on weight gain, energy expenditure, and body composition. Researchers conducted a single blind, randomized controlled trial of 25 U.S. adults. The subjects were healthy, weight-stable, male and female volunteers, aged 18 to 35 years. All subjects consumed a weight-stabilizing diet for 13 to 25 days. Afterwards, the researchers randomly assigned participants to diets containing various percentages of energy from protein: 5% (low protein), 15% (normal protein), or 25% (high protein). The subjects were not aware of the specific protein level diet to which they were assigned. On these diets the researchers overfed the participants during the last 8 weeks of their 10 to 12 week stay in the inpatient metabolic unit. The goal was to investigate the effect of overconsumption of protein on weight gain, energy expenditure, and body…arrow_forward
- A consumer advocacy group wanted to study whether different airline carriers differed in terms of their delayed flights. In particular, the researchers were interested in the relationship between p1, the proportion of Alpha Airlines flights that were delayed at least 15 minutes, and p2, the proportion of Beta Airlines flights that were delayed at least 15 minutes. A random sample of 1,000 Alpha flights and a separate random sample of 1,000 Beta flights found that 67 of the Alpha fights and 160 of the Beta flights were delayed at least 15 minutes. The conditions for inference were checked and verified. Does this set of samples provide strong evidence that Alpha Airlines has a smaller proportion of flights that are delayed at least 15 minutes than Beta Airlines, at the α = 0.05 significance level? Find the z-table here. A. The test statistic is z = –6.56 and the P-value ≈ 0. Since the P-value ≈ 0 < 0.05, there is not sufficient evidence that Alpha Airlines has fewer delayed…arrow_forwardDowns and Abwender (2002) evaluated soccer players and swimmers to determine whether the routine blows to the head experienced by soccer players produced long term neurological deficits. In the study, neurological tests were administered to mature soccer players and swimmers and the results indicated significant differences. In a similar study, a researcher obtained the following data. Swimmers Soccer Players 10 7 8 4 7 9 9 3 13 7 7 6 12 a)Are the neurological test scores significantly lower for the soccer player than for the swimmers in the control groups? Use a one-tailed test with = .05. b)Compute the value of r² (percentage of variance accounted for) these data.arrow_forwardA case–control study of patients on antihypertensive drugs related an increased risk of myocardial infarction (MI) for patients using calcium channel blockers (Psaty, et al.,1995). In this study, cases were antihypertensive drug patients who had suffered a first fatal or nonfatal MI through 1993, and controls were antihypertensive patients, matched by demographic factors, who had not suffered a MI. Among the comparisons reported were patients receiving calcium channel (CC) blockers (with and without diuretics) and patients receiving β–blockers (with and without diuretics). Results of numbers of patient by drug/MI status combination are given in Table 1. Compute the odds ratio of suffering MI (CC blockers relative to β–blockers), and the corresponding 95% CI. Does it appear that calcium channel blockers are associated with higher odds (and thus probability) of suffering MI than β –blockers? Table 1: Observed cell counts for antihypertensive drug/MI data Occurrence of…arrow_forward
- A study published in 2007 by Christopher Johnson, professor of music education and music therapy at the University of Kansas, revealed that students in elementary schools who took private music lessons scored around 20 percent higher in math scores on standardized tests, compared to students who did not take private music lessons. Is this a randomized experiment or an observational study? a) Randomized experiment, since researchers gave students standardized tests. b) Observational study, since whether the student took private music lessons was not randomly assigned. c) Observational study, since math scores were not randomly assigned. d) Observational study, since this was not a random sample.arrow_forwardIn randomized, double-blind clinical trials of a new vaccine, children were randomly divided into two groups. Subjects in group 1 received the new vaccine while subjects in group 2 received a control vaccine. After the second dose, 116 of 651 subjects in the experimental group (group 1) experienced fever as a side effect. After the second dose, 73 of 532 of the subjects in the control group (group 2) experienced fever as a side effect. Does the evidence suggest that a higher proportion of subjects in group 1 experienced fever as a side effect than subjects in group 2 at the α=0.10 level of significance? #1 Find the test statistic for this hypothesis test.arrow_forwardElizon Pharmaceuticals, Inc., announced the results of its first human trial of NPI 32101, a topical form of its skin ointment. A total of 225 patients diagnosed with skin irritations were randomly divided into three groups as part of a double-blind, placebo-controlled study to test the effectiveness of the new topical cream. The first group received a 0.5% cream, the second group received a 1.0% cream, and the third group received a placebo. Groups were treated twice daily for a 6-week period. (a)What type of experimental design is this? (b)What is the control group for this study? (c)What is the factor that is set to predetermined levels? What is the treatment? (d)What does it mean for this study to be double-blind? (e)Identify the experimental units. (f)Draw a diagram to illustrate the design.arrow_forward
- A study in Sweden looked at former elite soccer players, people who had played soccer but not at the elite level, and people of the same age who did not play soccer. Here is a two-way table that classifies these subjects by whether or not they had arthritis of the hip or knee by their mid-fifties: Elite Non-elite Did not play Arthritis 10 9 24 No arthritis 61 206 548 Based on this study, you can conclude thatarrow_forwardThe following is an abstract from the journal Exceptional Children (O’Connor, White, & Swanson, 2007): Abstract: This research evaluated two methods to improve the reading fluency of struggling readers. Poor readers in grades 2 and 4 with (n = 17) and without (n = 20) learning disabilities were randomly assigned to one of two fluency practice variations or to a control group. Students in the treatments practiced reading aloud under repeated or continuous reading conditions with an adult listener in 15-min sessions, 3 days per week for 14 weeks. For students in the treatment conditions, growth curve analyses revealed significant differences in fluency and reading comprehension over students in the control. We found no significant differences between practice conditions. Consider the following elements in this study: (1) poor readers (2) students in grades 2 and 4 (3) students with and without learning disabilities (4) reading aloud with an adult listener or not (5) repeated or…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_forward
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