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Researchers Sally Tracy and associates undertook a cross-sectional study looking at the method of delivery and cost of delivery for first-time "low risk" mothers under three delivery scenarios: (1) Caseload midwifery (2) Standard hospital care (3) Private obstetric care The results of the study revealed that \(58.5 \%\) of all births with midwifery were vaginal deliveries compared with \(48.2 \%\) of standard hospital births and \(30.8 \%\) of private obstetric care. In addition, the costs of delivery from midwifery was \(\$ 3903.78\) compared with \(\$ 5279.23\) for standard hospital care and \(\$ 5413.69\) for private obstetric care. Source: Sally K Tracy, Alec Welsh, Donna Hartz, Anne Lainchbury, Andrew Bisits, Jan White, and Mark Tracy "Caseload midwifery compared to standard or private obstetric care for first time mothers in a public teaching hospital in Australia: a cross sectional study of cost and birth outcomes" BMC Pregnancy and Childbirth 2014,14:46 (a) Why is this a cross-sectional observational study? (b) Name the explanatory variable in the study. (c) Name the two response variables in the study and determine whether each is qualitative or quantitative.

Classify the variable as qualitative or quantitative. Student ID number

Magnum, LLC, is a web page design firm that has two designs for an online hardware store. To determine which is the more effective design, Magnum uses one page in the Denver area and a second page in the Miami area. For each visit, Magnum records the amount of time visiting the site and the amount spent by the visitor. (a) What is the explanatory variable in this study? Is it qualitative or quantitative? (b) What are the two response variables? For each response variable, state whether it is qualitative or quantitative. (c) Explain how confounding might be an issue with this study.

You wonder whether green tea lowers cholesterol. (a) To research the claim that green tea lowers LDL (so-called bad) cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels. Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the non-green tea drinkers. Explain why this is an observational study. (b) Name some lurking variables that might exist in the study (c) Suppose, instead of surveying individuals regarding their tea-drinking habits, you decide to conduct a designed experiment. You identify 120 volunteers to participate in the study and decided on three levels of the treatment: a placebo, one cup of green tea daily, two cups of green tea daily. The experiment is to run for one year. The response variable will be the change in LDL cholesterol for each subject from the beginning of the study to the end. What type of experimental design is this? (d) Explain how you would use blinding in this experiment. (e) What is the factor? Is it qualitative or quantitative? (f) What factors might you attempt to control in this experiment. (g) Explain how to use randomization in this experiment. How does randomization neutralize those variables that are not controlled? (h) Suppose you assigned 40 subjects to each of the three treatment groups. In addition, you decided to control the variable exercise by having each subject perform 150 minutes of cardiovascular exercise each week by walking on a treadmill. However, the 40 subjects in the placebo group decided they did not want to walk on the treadmill and skipped the weekly exercise. Explain how exercise is now a confounding variable.

In Problems 11-22, identify the type of sampling used. A salesperson obtained a systematic sample of size 20 from a list of 500 clients. To do so, he randomly selected a number from 1 to 25 , obtaining the number \(16 .\) He included in the sample the 16 th client on the list and every 25 th client thereafter. List the numbers that correspond to the 20 clients selected.

Determine whether the quantitative variable is discrete or continuous. Goals scored in a season by a soccer plaver

The following abstract appears in The New England Journal of Medicine: BACKGROUND. The relation between passive smoking and lung cancer is of great public health importance. Some previous studies have suggested that exposure to environmental tobacco smoke in the household can cause lung cancer, but others have found no effect. Smoking by the spouse has been the most commonly used measure of this exposure. METHODS. In order to determine whether lung cancer is associated with exposure to tobacco smoke within the household, we conducted a case-control study of 191 patients with lung cancer who had never smoked and an equal number of persons without lung cancer who had never smoked. Lifetime residential histories including information on exposure to environmental tobacco smoke were compiled and analyzed. Exposure was measured in terms of "smokeryears," determined by multiplying the number of years in each residence by the number of smokers in the household. RESULTS. Household exposure to 25 or more smoker-years during childhood and adolescence doubled the risk of lung cancer. Approximately 15 percent of the control subjects who had never smoked reported this level of exposure. Household exposure of less than 25 smoker-years during childhood and adolescence did not increase the risk of lung cancer. Exposure to a spouse's smoking, which constituted less than one third of total household exposure on average, was not associated with an increase in risk. CONCLUSIONS. The possibility of recall bias and other methodologic problems may influence the results of casecontrol studies of environmental tobacco smoke. Nonetheless, our findings regarding exposure during early life suggest that approximately 17 percent of lung cancers among nonsmokers can be attributed to high levels of exposure to cigarette smoke during childhood and adolescence. (a) What is the research objective? (b) What makes this study a case-control study? Why is this a retrospective study? (c) What is the response variable in the study? Is it qualitative or quantitative? (d) What is the explanatory variable in the study? Is it qualitative or quantitative? (e) Can you identify any lurking variables that may have affected this study? (f) What is the conclusion of the study? Can we conclude that exposure to smoke in the household causes lung cancer? (g) Would it be possible to design an experiment to answer the research question in part (a)? Explain.

Determine whether the quantitative variable is discrete or continuous. Length (in minutes) of a country song

Determine whether the quantitative variable is discrete or continuous. Number of Sequoia trees in a randomly selected acre of Yosemite National Park

Determine whether the quantitative variable is discrete or continuous. High temperature on a randomly selected day in Memphis, Tennessee