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Chapter 1: Problem 10

For each of the statistical studies described, indicate whether the study is an observational study or an experiment. Give a brief explanation for your choice. A study to evaluate whether vitamins can help prevent recurrence of blocked arteries in patients who have had surgery to clear a blocked artery was described in the article "Vitamins Found to Help Prevent Blocked Arteries" (Associated Press, September 1, 2002). The study involved 205 patients who were assigned to one of two groups. One group received a vitamin supplement for 6 months, while the other group did not receive the vitamin supplement.

Short Answer

Expert verified
The provided study is an experiment, as the researchers manipulated the variable of interest, which was the intake of vitamin supplements.

Step by step solution

01

Identify the type of study

In the given example, the patients were divided into two groups: one that received vitamin supplements and the other that did not. Here, the variable being tested (i.e., intake of vitamin supplements) is under the researcher's control. The effects on the variable of interest (i.e., recurrence of blocked arteries) were then observed.
02

Make the determination

Given that the variable was manipulated by the researchers, the study can be classified as an experiment, not an observational study.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Observational Study
An observational study is a type of research where the investigator observes ongoing behavior without making any intervention. This means the researchers do not control or manipulate the variables.
In essence, an observational study lets nature take its course, with the researchers simply observing the outcomes and recording them.
  • For example, if you were observing a group of people to see how their diet choices affect heart health over time, and you didn't interfere with their diet, this would be an observational study.
  • The main advantage of observational studies is that they reflect real-world settings. However, the lack of control can make it difficult to determine a cause-and-effect relationship.
In our original problem, the study was actually an experiment because the researchers assigned different treatments to groups.
Variable Manipulation
Variable manipulation is a crucial element in experimental studies. By controlling and changing one or more variables, researchers can determine if these changes affect the outcome.
In experimental studies, one variable is typically kept constant, while another is changed to observe how it influences the results.
  • In our example study, the manipulated variable was the intake of vitamin supplements.
  • The ability to control variables allows researchers to establish a clearer cause-and-effect relationship between them.
When we see a study where researchers are actively changing the conditions being studied, it鈥檚 a strong indicator that we're looking at an experiment, not an observational study.
Blocked Arteries
Blocked arteries are a serious medical condition affecting heart health. Arteries can become blocked by the buildup of fatty deposits, known as plaque, which restricts blood flow.
This can lead to conditions like heart attacks or strokes if not managed properly.
  • Patients often undergo surgery to remove these blockages, but maintaining open arteries is crucial for ongoing heart health.
  • Post-surgery, strategies like lifestyle changes and medication or supplements can help prevent the recurrence of blockages.
  • In the original study, researchers investigated whether vitamins could aid in preventing such blockages after surgery, showcasing a proactive approach to heart health management.
Understanding and managing blocked arteries is essential for long-term cardiovascular health.

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Most popular questions from this chapter

For each of the statistical studies described indicate whether the study is an observational study or an experiment. Give a brief explanation for your choice. A paper appearing in The Journal of Pain (March 2010 , 199-209) described a study to determine if meditation has an effect on sensitivity to pain. Study participants were assigned to one of three groups. One group meditated for 20 minutes; one group performed a distraction task (working math problems!) for 20 minutes; and one group practiced a relaxation technique for 20 minutes. Sensitivity to pain was measured both before and after the 20-minute session.

1.24 The hand-washing behavior of adults using public restrooms at airports was the subject of a study conducted by the American Society of Microbiology. A press release issued by the Society (September 15,2003 ) included the following description: Although illnesses as deadly as SARS and as troublesome as the common cold or gastric distress can be spread hand-to-hand, the survey sponsored by the American Society of Microbiology (ASM) found that many people passing through major U.S. airports don't wash their hands after using the public facilities. More than 30 percent of people using restrooms in New York airports, 19 percent of those in Miami's airport, and 27 percent of air travelers in Chicago aren't stopping to wash their hands. The survey, conducted by Wirthlin Worldwide in August 2003 , observed 7,541 people in public washrooms in New York, Chicago, San Francisco, Dallas, Miami, and Toronto. These results were then generalized to people who use public restrooms. Answer the following four questions for this observational study. (Hint: Reviewing Examples 1.3 and 1.4 might be helpful.) a. What is the population of interest? b. Was the sample selected in a reasonable way? c. Is the sample likely to be representative of the population of interest? d. Are there any obvious sources of bias?

The article "Doctor Dogs Diagnose Cancer by Sniffing It Out" (Knight Ridder Newspapers, January 9, 2006) refers to an experiment described in the journal Integrative Cancer Therapies. In this experiment, dogs were trained to distinguish between people with breast and lung cancer and people without cancer by sniffing exhaled breath. Dogs were trained to lie down if they detected cancer in a breath sample. After training, the dogs' ability to detect cancer was tested using breath samples from people whose breath had not been used in training the dogs. The paper states, "The researchers blinded both the dog handlers and the experimental observers to the identity of the breath samples." Explain why this blinding is an important aspect of the design of this experiment.

The article "Yes that Miley Cyrus Biography Helps Learning" (The Globe and Mail, August 5,2010 ) describes an experiment investigating whether providing summer reading books to low-income children would affect school performance. Subjects in the experiment were 1,300 children randomly selected from first and second graders at low-income schools in Florida. A group of 852 of these children were selected at random from the group of 1,300 participants to be in the book group. The other 478 children were assigned to the control group. Children in the book group were invited to a book fair in the spring to choose any 12 reading books that they could then take home. Children in the control group were not given any reading books, but were given some activity and puzzle books. These children received books each year for three years until the children reached third and fourth grade. The researchers then compared reading test scores of the two groups. a. Explain why randomly selecting 852 of the 1,300 children to be in the book group is equivalent to random assignment of the children to the two experimental groups. b. Explain the purpose of including a control group in this experiment.

The paper "From Dr. Kildare to Grey's Anatomy" (Annals of Emergency Medicine [2010]: \(21 \mathrm{~A}-23 \mathrm{~A}\) ) describes several studies of how the way in which doctors are portrayed on television might influence public perception of doctors. One study was described as follows: Rebecca Chory, Ph.D., now an associate professor of communication at West Virginia University, began studying the effect of such portrayals on patients' attitudes toward physicians. Using a survey of 300 undergraduate students, she compared perceptions of physicians in 1992 - the end of the era when physicians were shown as all-knowing, wise father figures-with those in \(1999,\) when shows such as \(E R\) and Chicago Hope \((1994-2000)\) were continuing the transformation to showing the private side and lives of physicians, including vivid demonstrations of their weaknesses and insecurities. Dr. Chory found that, regardless of the respondents' personal experience with physicians, those who watched certain kinds of television had declining perceptions of physicians' composure and regard for others. Her results indicated that the more prime time physician shows that people watched in which physicians were the main characters, the more uncaring, cold, and unfriendly the respondents thought physicians were. a. Answer the following four questions for the observational study described in this exercise. (Hint: Reviewing Examples 1.3 and 1.4 might be helpful.) 1\. What is the population of interest? 2\. Was the sample selected in a reasonable way? 3\. Is the sample likely to be representative of the population of interest? 4\. Are there any obvious sources of bias? b. Based on the study design, do you think that the stated conclusions are reasonable?
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