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Chapter 9: Problem 14

Testosterone for Older Men. As men age, their testosterone levels gradually decrease. This may cause a reduction in lean body mass, an increase in fat, and other undesirable changes. Do testosterone supplements reverse some of these effects? A study in the Netherlands assigned 237 men aged 60 to 80 with low or low-normal testosterone levels to either a testosterone supplement or a placebo. The report in the Journal of the American Medical Association described the study as a "double-blind, randomized, placebo-controlled trial." 15 Explain each of these terms to someone who knows no statistics.

Short Answer

Expert verified
Double-blind means neither participants nor researchers know who gets the treatment. Randomized involves random assignment to groups. Placebo-controlled means one group gets a placebo to compare effects.

Step by step solution

01

Double-Blind Defined

In a double-blind study, neither the participants nor the researchers know which participants are receiving the actual treatment and which are receiving the placebo. This helps to prevent bias in the results, as neither party's expectations can influence the outcome of the study.
02

Randomized Explained

Randomized means the participants are randomly assigned to either the treatment group (testosterone supplement) or the control group (placebo). This random assignment minimizes pre-existing differences between the groups, ensuring that the effects observed in the study are due to the treatment itself and not other variables.
03

Placebo-Controlled Clarified

In a placebo-controlled study, one group receives the experimental treatment (testosterone supplement), while the other group receives a placebo, which is a substance with no therapeutic effect. The placebo group serves as a control, allowing researchers to assess the true effectiveness of the treatment by comparing results between the two groups.

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Key Concepts

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

Double-Blind Study
A double-blind study is a critical element in many scientific experiments, particularly in medical research. It means neither the participants nor the researchers know who is receiving the actual treatment and who is receiving a placebo. This is essential to ensure that the study's outcomes are not influenced by participants' or researchers' biases or expectations.

Without awareness of which group, they belong to, participants are less likely to experience changes simply because they believe they are being treated. Similarly, researchers cannot unconsciously interpret the data in favor of their desired outcome. This neutrality in observation and experience helps maintain the study's integrity and helps secure more reliable results.
  • Reduces bias
  • Balances expectations
  • Preserves study integrity
Randomized Controlled Trial
A randomized controlled trial (RCT) is the gold standard for testing the efficacy of new treatments. In an RCT, participants are randomly assigned to either the treatment group or the control group.

This randomness ensures that each group is similar at the start of the experiment, minimizing the effects of any external factors that could skew the results. By balancing potential variables between groups, researchers can confidently attribute any changes during the trial to the intervention being tested.

Why is this important? Randomization increases the credibility of the study findings, making conclusions more valid and convincing.
  • Ensures similar groups
  • Minimizes influence of external factors
  • Increases credibility of findings
Placebo-Control
In a placebo-controlled trial, one group receives the treatment while the other receives a placebo. The placebo is a substance with no therapeutic effect, often resembling the real treatment in appearance to maintain the study's blind status.

The purpose of a placebo is to provide a baseline to compare the treatment's actual effectiveness. By measuring differences and improvements between the treatment and placebo group, researchers can determine whether the treatment is genuinely effective or if the changes are due to psychological factors or the natural progression of a condition.

A placebo control is essential for accurately determining the true impact of the newly introduced treatment.
  • Provides a comparison baseline
  • Distinguishes real treatment effects from psychological impacts
  • Helps gauge true efficacy

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Most popular questions from this chapter

Marijuana and work. How does smoking marijuana affect willingness to work? Canadian researchers persuaded young adult men who used marijuana to live for 98 days in a "planned environment." The men earned money by weaving belts. They used their earnings to pay for meals and other consumption and could keep any money left over. One group smoked two potent marijuana cigarettes every evening. The other group smoked two weak marijuana cigarettes. All subjects could buy more cigarettes but were given strong or weak cigarettes, depending on their group. Did the weak and strong groups differ in work output and eamings? 29 (a) Outline the design of the experiment using 20 subjects with 10 assigned to each group. (b) Here are the names of the 20 subjects. Use software or Table B at line 126 to carry out the randomization your design requires. Abel Fleming Mani Scannell Aeffner Fritz Mattos Stout Birkel Giriunas Re铆chert Williams Bower Kennedy Riddle Wilso DeVore Lamone Sawant Worbis (c) Do you think this can be run as a double-blind experiment? Explain.

Does Meditation Reduce Anxiety? An experiment that claimed to show that meditation reduces anxiety proceeded as follows. The experimenter interviewed the subjects and rated their level of anxiety. Then the subjects were randomly assigned to two groups. The experimenter taught one group how to meditate, and they meditated daily for a month. The other group was simply told to relax more. At the end of the month, the experimenter interviewed all the subjects again and rated their anxiety level. The meditation group now had less anxiety. Psychologists said that the results were suspect because the ratings were not blind. Explain what this means and how lack of blindness could bias the reported results.

A marketing class designs two videos advertising an expensive Mercedes sports car. They test the videos by asking fellow students to view both (in random order) and say which makes them more likely to buy the car. Mercedes should be reluctant to agree that the video favored in this study will sell more cars because (a) the study used a matched pairs design instead of a completely randomized design. (b) results from students may not generalize to the older and richer customers who might buy a Mercedes. (c) this is an observational study, not an experiment.

The Community Intervention Trial for Smoking Cessation asked whether a communitywide advertising campaign would reduce smoking. The researchers located 11 pairs of communities, with each pair similar in location, size, economic status, and so on. One community in each pair was chosen at random to participate in the advertising campaign and the other was not. This is (a) an observational study. (b) a matched pairs experiment. (c) a completely randomized experiment.

Red meat and mortality. Many studies have found an association between red meat consumption and an increased risk of chronic diseases. What is the relationship between red meat consumption and mortality? A large study followed 120,000 men and women who were free of coronary heart disease and cancer at the beginning of the study. Participants were asked detailed questions about their eating habits every 4 years, and the study spanned almost 30 years. It was found that the risk of dying at an early age - from heart disease, cancer, or any other cause -rises with the amount of red meat that they consumed. 22 (a) Is this an observational study or an experiment? What are the explanatory and response variables? (b) The authors noted that "Men and women with higher intake of red meat were less likely to be physically active and were more likely to be current smokers, to drink alcohol, and to have a higher body mass index." Explain carefully why differences in these variables make it more difficult to conclude that higher intake of red meat explains the increased death rate. What are the variables physical activity, smoking status, drinking behavior, and body mass index called? (c) Suggest at least one lurking variable related to diet that may be confounded with higher intake of red meat. Explain why you chose these variables.
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