Concept explainers
Fish fights Alzheimer’s An AP story (July 22, 2003) described a study conducted over four years by Dr. Martha Morris and others from Chicago’s Rush-Presbyterian-St. Luke’s Medical Center involving 815 Chicago residents aged 65 and older (Archives of Neurology, July 21, 2003). Those who reported eating fish at least once a week had a 60% lower risk of Alzheimer’s than those who never or rarely ate fish. However, the story also quoted Dr. Rachelle Doody of Baylor College of Medicine as warning, “Articles like this raise expectations and confuse people. Researchers can show an association, but they can’t show cause and effect.” She said it is not known whether those people who had a reduced risk had eaten fish most of their lives, and whether other dietary habits had an influence. Using this example, describe how you would explain to someone who has never taken statistics (a) what a lurking variable is, (b) how there can be multiple causes for any particular response variable, and (c) why they need to be skeptical when they read new research results.
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Statistics: The Art and Science of Learning from Data (4th Edition)
- What is an experiment?arrow_forwardWhat is an experiment? Give two examples.arrow_forwardA research article describes a study that investigated the relationship between depression and chocolate consumption. Participants in the study were 931 adults who were not currently taking medication for depression. These participants were screened for depression using a widely used screening test. The participants were then divided into two samples based on their test score. One sample consisted of people who screened positive for depression, and the other sample consisted of people who did not screen positive for depression. Each of the study participants also completed a food frequency survey. The researchers believed that the two samples were representative of the two populations of interest—adults who would screen positive for depression and adults who would not screen positive. The paper reported that the mean number of servings per month of chocolate for the sample of people that screened positive for depression was 8.37, and the sample standard deviation was 14.85. For the…arrow_forward
- Car Window Skin Cancer? A study suggests that exposure to UV rays through the car window may increase the risk of skin cancer. The study reviewed the records of all 1050 skin cancer patients referred to the St. Louis University Cancer Center in 2004. Of the 42 patients with melanoma, the cancer occurred on the left side of the body in 31 patients and on the right side in the other 11. A. Is this an experiment or an observational study? B. Of the patients with melanoma, what proportion had the cancer on the left side? Show what numbers you divide and give answer to 3 decimal places. C. A bootstrap 95% confidence interval for the proportion of melanomas occurring on the left is 0.579 to 0.861. Clearly interpret the confidence interval in the context of the problem. D. Suppose the question of interest is whether melanomas are more likely to occur on the left side than on the right. That is, are over 50% of melanomas on the left side? Ho: p = 0.5 Ha: p > 0.5 Use the confidence interval…arrow_forwardEach year, over 2 million people in the United States become infected with bacteria that are resistant to antibiotics. In particular, the Centers of Disease Control and Prevention has launched studies of drug-resistant gonorrhea (CDC.gov website). Of 142 cases tested in Alabama, 9 were found to be drug-resistant. Of 268 cases tested in Texas, 5 were found to be drug-resistant. Do these data suggest a statistically significant difference between the proportions of drug-resistant cases in the two states? Use a 0.02 level of significance. What is the p-value, and what is your conclusion? Test statistic = (to 2 decimals) p-value = (to 4 decimals) Conclusion: Select your answer - Choose the correct option. There is a significant difference in drug resistance between the two states. Alabama has the higher drug resistance rate. - Select your answer - ▼arrow_forwardEach year, over 2 million people in the United States become infected with bacteria that are resistant to antibiotics. In particular, the Centers of Disease Control and Prevention has launched studies of drug-resistant gonorrhea (CDC.gov website). Of 142 cases tested in Alabama, 9 were found to be drug-resistant. Of 268 cases tested in Texas, 5 were found to be drug-resistant. Do these data suggest a statistically significant difference between the proportions of drug-resistant cases in the two states? Use a 0.02 level of significance. What is the p-value, and what is your conclusion?arrow_forward
- A 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_forwardUrban legend says that knuckle cracking is bad for you and will eventually lead to osteoarthritis of the hand joints. A retrospective case-control study of individuals who had received an X-ray of the right hand in the past 5 years enrolled 180 subjects with a confirmed diagnosis of hand osteoarthritis and 95 control subjects in the same age group. The study found that 36 subjects with hand osteoarthritis and 25 control subjects were habitual knuckle crackers. Is there good evidence that the proportion of knuckle crackers is greater among individuals with hand osteoarthritis? Does this support the urban legend about knuckle cracking?arrow_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 800 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 28 38 100 No 182 126 392 700 Total 216 154 430 800 • Given: The value of the test statistic is x? = 11.894. Use a = 0.1 as the level of significance.arrow_forward
- As part of a long-term study of individuals 65 years of age or older, sociologists and physicians at the Wentworth Medical Center in upstate New York investigated the relationship between geographic location and depression. A sample of 60 individuals, all in reasonably good health, was selected; 20 individuals were residents of Florida, 20 were residents of New York, and 20 were residents of North Carolina. Each of the individuals sampled was given a standardized test to measure depression. Higher test scores indicate higher levels of depression. A second part of the study considered the relationship between geographic location and depression for individuals 65 years of age or older who had a chronic health condition such as arthritis, hypertension, and/or heart ailment. A sample of 60 individuals with such conditions was identified. Again, 20 were residents of Florida, 20 were residents of New York, and 20 were residents of North Carolina. Prepare a managerial report that summarizes…arrow_forwardSample surveys show that more people are tracking changes in their health on paper, spreadsheet, mobile device, or just "in their heads." A survey asked a nationwide random sample of 3014 adults, "Now thinking about your health overall, do you currently keep track of your own weight, diet, or exercise routine, or is this not something you currently do?" The population that the poll wants to draw conclusions about is all U.S. residents aged 18 or over. Suppose that, in fact, 61% of all adult U.S. residents would say "Yes" if asked this question. Using Table A, find the (approximate) probability that 1900 or more adults in the sample say "Yes." (Enter your answer rounded to four decimal places.)arrow_forward"Bullying," according to noted expert Dan Olweus, "poisons the educational environment and affects the learning of every child." Bullying and victimization are evident as early as preschool, with the problem peaking in middle school. Suppose you are interested in the emotional well-being of not only the victims but also bystanders, bullies, and those who bully but who are also victims (bully-victims). You decide to measure depression in a group of victims and a group of bully-victims using a 26-item, 3-point depression scale. Assume scores on the depression scale are normally distributed and that the variances of the depression scores are the same among victims and bully-victims. The group of 25 victims scored an average of 25.3 with a sample standard deviation of 9 on the depression scale. The group of 23 bully-victims scored an average of 20.5 with a sample standard deviation of 8 on the same scale. You do not have any presupposed assumptions about whether victims or bully-victims…arrow_forward
- Glencoe Algebra 1, Student Edition, 9780079039897...AlgebraISBN:9780079039897Author:CarterPublisher:McGraw HillBig Ideas Math A Bridge To Success Algebra 1: Stu...AlgebraISBN:9781680331141Author:HOUGHTON MIFFLIN HARCOURTPublisher:Houghton Mifflin HarcourtCollege Algebra (MindTap Course List)AlgebraISBN:9781305652231Author:R. David Gustafson, Jeff HughesPublisher:Cengage Learning