Friis Chapter 8, Questions 3, 8, & 9
3. Explain the purposes of blinding and randomization in clinical trials. (2 points, 1 for blinding and 1 for randomization)
8. Epidemiologic studies of the role of a suspected factor in the etiology of a disease may be observational or experimental. Which of the following is the essential difference between experimental and observational studies? In experimental studies… (1 point)
The study and control groups are equal in size.
The study is prospective.
The study and control groups are always comparable with respect to all factors other than the exposure.
The investigator determines who shall be exposed to the suspected factor and who shall not.
Controls are used.
9. From the descriptions provided, identify the type of study design. Note that a particular study design may be the correct answer more than once.
Smoking histories are obtained from all patients entering a hospital who have lip cancer and are compared with smoking histories of patients with cold sores who enter the same hospital. (1 point)
The entire population of a given community is examined, and all who are judged free of bowel cancer are questioned extensively about their diet. These people are then followed for several years to see whether their eating habits will predict their risk of developing bowel cancer. (1 point)
To test the efficacy of vitamin C in preventing colds, army recruits are randomly assigned to two groups: one given 500 mg of vitamin C daily, and one given a placebo. Both groups are followed to determine the number and severity of subsequent colds. (1 point)
The physical examination records of the incoming first-year class of 1935 at the University of Minnesota are examined in 1980 to see whether the freshmen’s recorded height and weight at the time of admission to the university were related to their chance of developing coronary heart disease by 1981. (1 point)
A total of 1,500 adult men who worked for Lockheed Aircraft were initially examined in 1951 and were classified by diagnostic criteria for coronary artery disease. Every three years, they have been reexamined for new cases of the disease; attack rates in different subgroups have been computed annually. (1 point)
A random sample of middle-aged sedentary women was selected from four census tracts, and each subject was examined for evidence of osteoporosis. Those found to have the disease were excluded. All others were randomly assigned to either an exercise group, which followed a two-year program of systematic exercise, or a control group, which had no exercise program. Both groups were observed semiannually for incidence of osteoporosis. (1 point)
Questionnaires were mailed to every 10th person listed in the city telephone directory. Each person was asked to provide his or her age, sex, and smoking habits and to describe the presence of any respiratory symptoms during the preceding 7 days. (1 point)
Critical Appraisal Exercise
Read this article from Polack et al: Safety and Efficacy of the BNT162b2 mRNA Covid-19 VaccineActions (New England Journal of Medicine, 2020). Note that it is a more advanced RCT and can be difficult to read, so I have highlighted the areas I would like you to focus on in yellow.
Select 1-4 sentences from the text of the Polack et al articleActions that exemplifies each of the following concepts (you may copy and paste from the article to answer these questions):
What is the study objective? (1 point)
Did participants give informed consent? (1 point)
What is the eligibility criteria for participating in the study? (1 point)
What is the intervention being tested? (1 point)
What is the intervention group being compared to? (1 point)
What is the primary outcome of the study? (1 point)
What is the study’s conclusion? (1 point)
What are the main limitations of the study? (1 point)
Complete the bolded items (items 1, 3-8, 10) in the JBI checklist for critical appraisal of randomized controlled trialsActions (RCTs) for the Polack et al studyActions . (8 points)
Evidence-Based Public Health
Reflect on the term “evidence-based public health,” as discussed in this week’s assigned article from Brownson et alActions . In your own words, how do you define it? (1 point) What role does evidence-based public health play in our everyday lives? (1 point) In your opinion, what is the biggest barrier to implementing evidence-based public health policies? (1 point)
Explain the purposes of blinding and randomization in clinical trials.
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