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Chapter 1: Q 8. (page 32)
Identify and explain the significance of the three basic principles of experimental design.
Control, Randomization, and Replication are the three basic principles of experimental design.
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In Exercises 1.17-1.22, state whether the investigation in question is an observational study or a designed experiment. Justify your answer in each case.
Aspirin and Cardiovascular Disease. In the article by P. Ridker et al. titled "A Randomized of Low-dose Aspirin in the Primary Prevention of Cardiovascular Disease in Women" (New England Journal of Medicine, Vol. 352, pp. 1293–1304), the researchers noted that "We randomly assigned 39,876 initially healthy women 45 years of age or older to receive 100 mg of aspirin or placebo on alternate days and then monitored them for 10 years for a first major cardiovascular event (i.e., nonfatal myocardial infarction, non-fatal stroke, death from cardiovascular causes)."
Adverse Effects of Prozac. Prozac ( fluoxetine hydrochloride ), a product of Eli Lilly and Company, is used for the treatment of depression, obsessive-compulsive disorder ( OCD ), and bulimia nervosa. An issue of the magazine Arthritis Today contained an advertisement reporting on the " ... treatment-emergent adverse events that occurred in 2 % or more patients treated with Prozac and with incidence greater than placebo in the treatment of depression, OCD, or bulimia. " In the study, 2444 patients took Prozac and 1331 patients were given placebo. Identify the
(a) treatment group.
(b) control group.
(c) treatments.
Lifetimes of Flashlight Batteries.Two different options are under consideration for comparing the lifetimes of four brands of flashlight battery, using 20 flashlights.
(a) One option is to randomly divide 20 flashlights into four groups of 5 flashlights each and then randomly assign each group to use a different brand of battery. Would this statistical design be a completely randomized design or a randomized block design? Explain your answer.
(b) Another option is to use 20 flashlights - five different brands of 4 flashlights-each and randomly assign the 4 flashlights of each sign be a completely randomized design or a randomized block design? Explain your answer.
Best-Selling Albums. Refer to Exercise 1.44.
(a). List the 15 possible samples (without replacement) of four artists that can be selected from the six.
(b). Describe a procedure for taking a simple random sample of four artists from the six.
(c). If a simple random sampling procedure is used to obtain four artists, what are the chances of selecting E, A, L, and B? P, B, M, and A?
In Exercises 1.17-1.22, state whether the investigation in question is an observational study or a designed experiment. Justify your answer in each case.
Heart Failure. In the paper "Cardiac-Resynchronization Therapy with or without an Implantable Defibrillator in Advanced Chronic Heart Failure" (New England Journal of Medicine, Vol. 350, pp. 2140-2150), M. Bristow et al. reported the results of a study of methods for treating patients who had advanced heart failure due to ischemic or nonischemic cardiomyopathies. A total of 1520 patients were randomly assigned in a 1:2:2 ratio to receive optimal pharmacologic therapy alone or in combination with either a pacemaker or a pacemaker-defibrillator combination. The patients were then observed until they died or were hospitalized for any cause.
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