Chapter 1: Q 4. (page 31)
Before planning and conducting a study to obtain information, what should be done?
Literature study is a must before planning and conducting a study.
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Peanut Allergies. In the article " Food Allergy Advice May Be Peanuts " (Science News, Vol . 174, No. 12, pp . 8-9), N. Seppa reports that early exposure to peanuts seems to lessen the risk of nut allergy. Of 4000 Jewish children sampled in Britain, 1.85 % had peanut allergies; and of 4600 Jewish children sampled in Israel, where early peanut consumption is more common, 0.17 % had peanut allergies. The researcher chose Jewish children in both countries to limit genetic differences between groups.
(a) Is this study descriptive or inferential?
(b) Is this study observational or experimental?
Causes of Death. The National Center for Health Statistics published the following data on the leading causes of death in 2010 in National Vital Statistics Reports. Deaths are classified according to the tenth revision of the International Classification of Diseases.
Rates are per 100,000 population.
Comparing Gas Mileages. An experiment is to be conducted to compare four different brands of gasoline for gas mileage.
(a) Suppose that you randomly divide 24 cars into four groups of 6 cars each and then randomly assign the four groups to the four brands of gasoline, one group per brand. Is this experimental design a completely randomized design or a randomized block design? If it is the latter, what are the blocks?
(b) Suppose, instead, that you use six different models of cars whose varying characteristics (e.g., weight and horsepower) affect gas mileage. Four cars of each model are randomly assigned to the four different brands of gasoline. Is this experimental design a completely randomized design or a randomized block design? If it is the latter, what are the blocks?
(c) Which design is better, the one in part (a) or the one in part (b)? Explain your answer.
Explain why a census is often not the best way to obtain information about a population.
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.
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