The authors of the paper “Influence of Biofeedback Weight Bearing Training in Sit to Stand to Sit and the Limits of Stability on Stroke Patients” (The Journal of Physical Therapy Science [2016]: 3011–3014) randomly selected two samples of patients admitted to the hospital after suffering a stroke. One sample was selected from patients who received biofeedback weight training for 8 weeks, and the other sample was selected from patients who did not receive this training. At the end of 8 weeks, the time it took (in seconds) to stand from a sitting position and then to sit down again (called sit-stand-sit time) was measured for the people in each sample. Data consistent with summary quantities given in the paper are given below. For purposes of this exercise, you can assume that the samples are representative of the population of stroke patients who receive the biofeedback training and the population of stroke patients who do not receive this training. Use the given data to construct and interpret a 95% confidence interval for the difference in
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Chapter 11 Solutions
Introduction To Statistics And Data Analysis
- What is an experiment?arrow_forwardIt is common for baseball pitchers to use stretching to prepare for a game. But does this make a difference? The authors of a paper on the effects of stretching in baseball carried out an experiment to compare two different types of stretching and a control treatment consisting of no stretching. Participants were adult males with varying levels of baseball throwing experience and who were not professional or collegiate baseball players. Participants in the two stretching treatments went through a warm-up that included 8 minutes of stretching. Each participant (all three groups) then threw 10 pitches, and the average speed (km/hour) was calculated. (a) Explain why it is important that the participants be assigned at random to the three different treatment groups (Stretching Method 1, Stretching Method 2, and No Stretching). Random assignment ensures that our experiment systematically favors one experimental condition over all others and attempts to create experimental groups that are as…arrow_forwardStressed-Out Bus Drivers. Previous studies have shown that urban bus drivers have an extremely stressful job, and a large proportion of drivers retire prematurely with disabilities due to occupational stress. In the paper, “Hassles on the Job: A Study of a Job Intervention With Urban Bus Drivers” (Journal of Organizational Behavior, Vol. 20, pp. 199–208), G. Evans et al. examined the effects of an intervention program to improve the conditions of urban bus drivers.Amongother variables, the researchers monitored diastolic blood pressure of bus drivers in downtown Stockholm, Sweden. The data, in millimeters of mercury (mm Hg), on the WeissStats site are based on the blood pressures obtained prior to intervention for the 41 bus drivers in the study. Use the technology of your choice to do the following. a. Obtain a normal probability plot, boxplot, histogram, and stemand-leaf diagram of the data. b. Based on your results from part (a), can you reasonably apply the one-mean t-test to the…arrow_forward
- A Canadian study measuring depression level in teens (as reported in the Journal of Adolescence, vol. 25, 2002) randomly sampled 112 male teens and 101 female teens, and scored them on a common depression scale (higher score representing more depression). The researchers suspected that the mean depression score for male teens is higher than for female teens, and wanted to check whether data would support this hypothesis. What conclusion can you draw from the output? The data provide sufficient evidence to reject H0 and to conclude that the mean depression score for male teens is larger than that of female teens. The data provide sufficient evidence to conclude that male and female teens do not differ in mean depression score. The data do not provide sufficient evidence to conclude that the mean depression score of male teens is larger than that of female teens. The data do not provide sufficient evidence to reject H0, so we accept it, and conclude that male and female teens do…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_forwardIs Seat Belt Use Independent of Cigarette Smoking?A study of seat belt users and nonusers yielded the randomly selected sample data summarized in the given table (based on data from “What Kinds of People Do Not Use Seat Belts?” by Helsing and Comstock,American Journal of Public Health,Vol. 67, No. 11). Test the claim that the amount of smoking is independent of seat belt use. A plausible theory is that people who smoke more are less concerned about their health and safety and are therefore less inclined to wear seat belts. Is this theory supported by the sample data?arrow_forward
- Female college student participation in athletics has increased dramatically over the past few decades. Sports medicine providers are aware of some unique health concerns of athletic women, including disordered eating. A study compared disordered-eating symptoms and their causes for collegiate female athletes (in lean and non lean sports) and nonathletes. The sample mean of the body dissatisfaction assessment score was 13.4 (s=7.9) for 15 lean sports athletes (those sports that place value on leanness, including distance running, swimming, and gymnastics) and 7.4 (s=5.8) for the 67 non-lean athletes. Assume equal population standard deviations. Find the standard error for comparing the means. Construct a 95% confidence interval for the difference between the mean body dissatisfaction for lean sport athletes and non lean sport athletes. Interpret.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_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
- In Hong Kong, some employers claim that they are willing to offer betterstarting salaries for those university graduates with a higher GPA. A study on Hong Kong university students was carried out. A simple random sample of 96 students who were admitted to Hong Kong universities between 2010 and 2013 was selected. Final cumulative GPA and starting salary (monthly salary in Hong Kong Dollars) of each participant were collected. A scatterplot of the two variables (gpa = final cumulative GPA; salary = starting salary) is shown below.arrow_forwardA study (Journal of Family Practice 2000; 50:138-144) with 233 low-income adult smokers evaluated the effectiveness of usual care (physician advice and follow-up) for smokers wishing to quit to the usual care enhanced by computer-assisted telephone counseling sessions. Each subject was assigned randomly either to the usual care or to the usual care plus counseling, and their smoking status (still smoking or quit smoking) was observed after 3 months. The percentage who had quit smoking was higher for the group receiving counseling. (a) Identify the response variable and the explanatory variable. Response: ---Select--- type of care income level quit smoking or not time until quit smoking Explanatory: ---Select--- type of care income level quit smoking or not time until quit smoking (b) Is this study an observational study or an experiment? Explain. Observational study. Smokers were not randomly assigned to care groups. Observational study. Smokers were randomly…arrow_forwardWorker Fatigue. A study by M. Chen et al. titled “Heat Stress Evaluation andWorker Fatigue in a Steel Plant” (American Industrial Hygiene Association, Vol. 64, pp. 352–359) assessed fatigue in steelplant workers due to heat stress. Among other things, the researchers monitored the heart rates of a random sample of 29 casting workers. A hypothesis test is to be conducted to decide whether the mean postwork heart rate of casting workers exceeds the normal resting heart rate of 72 beats per minute (bpm). a. determine the null hypothesis. b. determine the alternative hypothesis. c. classify the hypothesis test as two tailed, left tailed, or right tailed.arrow_forward
- Holt Mcdougal Larson Pre-algebra: Student Edition...AlgebraISBN:9780547587776Author:HOLT MCDOUGALPublisher:HOLT MCDOUGALBig Ideas Math A Bridge To Success Algebra 1: Stu...AlgebraISBN:9781680331141Author:HOUGHTON MIFFLIN HARCOURTPublisher:Houghton Mifflin HarcourtGlencoe Algebra 1, Student Edition, 9780079039897...AlgebraISBN:9780079039897Author:CarterPublisher:McGraw Hill