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Chapter 1: Q 1.20. (page 8)

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鈥�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)."

Short Answer

Expert verified

The investigation in question is a Designed Experiment.

Step by step solution

01

Step 1. Given information.

The given investigation is:

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鈥�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.

02

Step 2. State whether the given investigation is an observational study or a designed experiment.

The study in question is a Designed Experiment. The researchers used treatment and control groups on 39.876 women aged 45 and over, and followed them for a decade. The qualities were then observed and measurements collected.

We know that a designed experiment is applying treatments to experimental units, controlling extraneous sources of variation that could affect the experiment, and then observing features and taking measurements on the experimental units.

Therefore, the investigation in question is a Designed Experiment.

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Most popular questions from this chapter

Oklahoma State Officials. The five top Oklahoma state officials are displayed in Table 1.2 on page 11. Use that table to solve the following problems.

(a). List the 10 possible samples (without replacement) of size 3 that can be obtained from the population of five officials.

(b). If a simple random sampling procedure is used to obtain a sample of three officials, what are the chances that it is the first sample on your list in part (a)? the second sample? the tenth sample?

In a designed experiment, there are two factors, say, Factor Aand Factor B. Factor Ahas four levels, say, a1,a2,a3anda4; Factor B has two levels, say,b1andb2.

(a) Construct a schematic for the treatments similar to Table 1.8 on page 27.

(b) Use part ( a ) to determine the number of treatments.

(c) Could you have determined the answer for part ( b ) without constructing the schematic in part ( a )? Explain your answer.

In Exercises 1.92-1.97, we present descriptions of designed experiments. In each case, identify the

(a) experimental units

(b) response variable

(c) factor (s)

(d) levels of each factor:-

(e) treatments.

Dexamethasone and IQ. In the paper "Outcomes at School Age After Postnatal Dexamethasone Therapy for Lung Disease of Prematurity" (New England Journal of Medicine,Vol . 350, No. 13, pp . 1304-1313), T. Yeh et al . studied the outcomes at school age in children who had participated in a double-blind, placebo-controlled trial of early postnatal dexamethasone therapy for the prevention of chronic lung disease of prematurity. One result reported in the study was that, at school age, the control group of 74 children had an average IQ score of 84.4, whereas the dexamethasone group of 72 children had an average IQ score of 78.

Oklahoma State Officials. Refer to Table 5.1 on page 196.

(a). List the possible samples without replacement of size 4 that can be obtained from the population of five officials. (Hint: There are five possible samples.)

If a simple random sample without replacement of four officials is taken from the five officials, determine the probability that

(b). the governor, secretary of state, attorney general, and treasurer are obtained.

(c). the governor and treasurer are included in the sample.

(d). the governor is included in the sample.

Dental Hygiene: Which Toothbrush? In an experiment reported by J. Singer and D. Andrade in the article " Regression Models for the Analysis of Pretest / Posttest Data " ( Biometrics, Vol . 53, pp . 729-735 ), the effect of using either a conventional or experimental ( hugger ) toothbrush was investigated. Twelve female and 12 male preschoolers were selected. Within each gender group, six were randomly assigned to the conventional toothbrush and the remaining six to the experimental toothbrush. After each subject brushed with the assigned toothbrush, a dental plaque index was measured. The higher the dental plaque index, the greater was the amount of plaque on an individual's teeth.

(a) Is the statistical design described here a completely randomized design or a randomized block design? Explain your answer.

(b) If the statistical design is a randomized block design, what are the blocks?
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