Exercises

EXERCISES

1.1 What is your current job or future career objective? How can an understanding of statistics be helpful in your career?

1.2 What are some job roles for statisticians in the health field?

1.3 Compare and contrast descriptive and inferential statistics. How are they related?

1.4 Explain the major difference between prospective and retrospective studies. Does one have advantages over the other?

1.5 What is the difference between observational and experimental studies? Why do we conduct experimental studies? What is the purpose of observational studies?

1.6 What are cross-sectional studies? What types of questions can they address?

1.7 Why are quality control methods important to manufacturers? List at least three quality control methods discussed in the chapter.

1.8 Clinical trials play a vital role in testing and development of new drugs and medical devices.

a. What are clinical trials?

b. Explain the difference between controlled and uncontrolled trials.

c. Why are controls important?

d. What are single and double blinding? How is blinding used in a clinical trial?

e. What types of outcomes for patients are measured through the use of clinical trials? Name at least four.

1.9 Epidemiology, a fundamental discipline in public health, has many applications in the health sciences.

a. Name three types of epidemiologic study designs.

b. What types of problems can we address with them?

1.10 Suppose a health research institute is conducting an experiment to determine whether a computerized, self-instructional module can aid in smoking cessation.

a. Propose a research question that would be relevant to this experiment.

b. Is there an independent variable (exposure factor) in the institute’s experiment?

c. How should the subjects be assigned to the treatment and control groups in order to minimize bias?

1.11 A pharmaceutical company wishes to develop and market a new medication to control blood sugar in diabetic patients. Suggest a clinical trial for evaluating the efficacy of this new medication.

a. Describe the criteria you would use to select cases or patients.

b. Is there a treatment to compare with a competing treatment or against a placebo?

c. How do you measure effectiveness?

d. Do you need to address the safety aspects of the treatment?

e. Have you planned an early stopping rule for the trial if the treatment appears to be unsafe?

f. Are you using blinding in the trial? If so, how are you implementing it? What problems does blinding help you avoid?

1.12 Search the Web for a media account that involves statistical information. For example, you may be able to locate a report on a disease, a clinical trial, or a new medical device. Alternatively, if you do not have access to the Web, newspaper articles may cover similar topics. Sometimes advertisements for medicines present statistics. Select one media account and answer the following questions:

a. How were the data obtained?

b. Based on the information presented, do you think that the investigators used a descriptive or inferential approach?

c. If inferences are being drawn, what is the main question being addressed?

d. How was the sample selected? To what groups can the results be generalized?

e. Could the results be biased? If so, what are the potential sources of bias?

f. Were conclusions presented? If so, do you think they were warranted? Why or why not?

1.13 Public interest groups and funding organizations are demanding that clinical trials include diverse study populations—from the standpoint of age, gender, and ethnicity. What do you think is the reasoning behind this demand? Based on what you have read in this chapter as well as your own experiences, what are the advantages and disadvantages of using diverse study groups in clinical trials?

Answer:

1.6 Cross-sectional studies are studies on a population at a fixed point in time. Many surveys are cross-sectional. They are used to measure current thinking or the opinion at a particular time that interests the investigator. An opinion poll on candi-dates in an election just before (a day or two) election might be used to predict the winner. Such a poll taken a few months before the election could be used by a par-ticular candidate to gauge further campaign strategy.

1.8 a. Clinical trials are studies over time that follow patients to determine the safety and effectiveness of a particular experimental treatment. In clinical trials, pa-tients are usually randomized to various treatment groups (at least two). One group may be given a placebo or an active control treatment for comparison. Blinding is often done and double-blinding is often preferred.

b. Controlled trials are trials that include randomization and a control group. Uncontrolled trials are missing either randomization or the control or both.

c. Controls are important to get objective comparison, to avoid bias and/or ad-just for a “placebo effect.”

d. Blinding is a technique that keeps the patient and often the investigator from knowing which treatment the patient is getting. It is implemented through random-ization codes that are used to assign the treatments to the patients but are not known to the investigator or the patient. At the end of the trial, these codes are used to match the patients to their treatments for the statistical analysis.

e. Here are some outcomes that are measured in clinical trials:

1. Patient satisfaction with the treatment

2. Patient reported quality of life questions

3. Comparison of glycemic control for diabetic patients between a new treat-ment and an active control

4. Adverse events occurring during the trial

5. Ability of a diabetes drug to lower cholesterol as well as control glucose levels

6. Acute success rate for an ablation procedure with an experimental catheter and procedure compared to a control catheter and standard treatment.

7. Six-month capture threshold comparison of patients with a pacemaker with steroid-eluting leads compared to control group patients with a pace-maker that has a nonsteroid lead

8. Comparison of survival times for AIDS patients getting a new therapy ver-sus AIDS patients getting standard treatment