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Chapter 1: Q 1.19. (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.

Sex, Sleep, and PTSD. In the article, "One's Sex, Sleep, and Posttraumatic Stress Disorder" (Biology of Sex Differences, Vol. 3, No. 29, pp. 1-7), I. Kobayashi et al. study the relationship between one's sex, sleep patterns, and posttraumatic stress disorder (PTSD) after trauma exposure. The authors report that women have a higher lifetime prevalence of PTSD as well as a greater risk of developing PTSD following trauma exposure. Relationships between sleep and physical health have been documented in a number of studies, and the authors explore the possibility that disruptive sleep habits are common among people with PTSD and also a possible risk factor for the development of PTSD. A questionnaire of men and women with and without PTSD produced data on their sleep habits.

Short Answer

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The given investigation is an observational study.

Step by step solution

01

Step 1. Given information.

The given statement is:

In the article, "One's Sex, Sleep, and Posttraumatic Stress Disorder" (Biology of Sex Differences, Vol. 3, No. 29, pp. 1-7), I. Kobayashi et al. study the relationship between one's sex, sleep patterns, and posttraumatic stress disorder (PTSD) after trauma exposure. The authors report that women have a higher lifetime prevalence of PTSD as well as a greater risk of developing PTSD following trauma exposure. Relationships between sleep and physical health have been documented in a number of studies, and the authors explore the possibility that disruptive sleep habits are common among people with PTSD and also a possible risk factor for the development of PTSD. A questionnaire of men and women with and without PTSD produced data on their sleep habits.

02

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

The researchers in this study gathered information on men's and women's sleeping patterns.

In other words, the researchers look at both males and women with post-traumatic stress disorder (PTSD). The individuals are also not subjected to any therapy by the researchers.

As a result, the research issue is an observational study.

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Most popular questions from this chapter

In a designed experiment, there are two factors, say, Factor Aand Factor B. Factor Ahas three levels, say, a1,a2anda3; Factor Bhas four levels, say,b1,b2,b3andb4.

(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.

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.

Identify two methods for obtaining a simple random sample.

Hepatitis B and Pancreatic Cancer.The article "Study Links Hepatitis B and Cancer of Pancreas" by D. Grady, appeared in the September 29, 2008 issue of the New York Times. It reported that, for the first time, a study showed that people with pancreatic cancer are more likely than those without the disease to have been infected with the hepatitis B virus. The study by M. Hassan et al . , titled "Association Between Hepatitis B Virus and Pancreatic Cancer" (Journal of Clinical Oncology, Vol. 26, No. 28, pp. 4557-4562) compared 476 people who had pancreatic cancer with 879 healthy control subjects. All were tested to see whether they had ever been infected with the viruses that cause hepatitis B or hepatitis C. The results were that no connection was found to hepatitis C, but the cancer patients were twice as likely as the healthy subjects to have had hepatitis B. The researchers noted, however, that "...while the study showed an association, it did not prove cause and effect. More work is needed to determine whether the virus really can cause pancreatic cancer." Explain the validity of the statement in quotes.

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