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An article in the San Luis Obispo Tribune (September \(7,\) 1999) described an experiment designed to investigate the effect of creatine supplements on the development of muscle fibers. The article states that the researchers "looked at 19 men, all about 25 years of age and similar in weight, lean body mass, and capacity to lift weights. Ten were given creatine -25 grams a day for the first week, followed by 5 grams a day for the rest of the study. The rest were given a fake preparation. No one was told what he was getting. All the men worked out under the guidance of the same trainer. The response variable measured was gain in fat-free mass (in percent)." a. What extraneous variables are identified in the given statement, and what strategy did the researchers use to deal with them? b. Do you think it was important that the men participating in the experiment were not told whether they were receiving creatine or the placebo? Explain. c. This experiment was not conducted in a double-blind manner. Do you think it would have been a good idea to make this a double-blind experiment? Explain.

Step by step solution

01

Identify Extraneous Variable

Extraneous variables are the variables that could affect the outcome of the experiment but are not the variables being studied. In this case, the extraneous variables identified are the men's age, weight, lean body mass and capacity to lift weights. The researchers mitigated these by selecting a group of men who are all about the same age, have similar body types and lifting capacities.

02

Importance of Blinding Participants

The purpose of blinding the men to their treatment (whether they were receiving creatine or a placebo) was to prevent bias in the results. If the men knew what they were receiving, this knowledge might influence their behavior or self-evaluations of their muscle mass changes, which could lead to skewed results

03

Importance of Double-blind Study

The lack of a double-blind design in this experiment means that the researchers knew which participants were receiving creatine and which were receiving placebo. This can potentially introduce bias into the experiment, as researchers may, even unwittingly, treat participants differently or interpret results differently based on their treatment. Therefore, it would have been a good idea to implement a double-blind design where both parties are not informed about the treatment.

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Key Concepts

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

Extraneous Variables

In experimental design, extraneous variables are factors that can inadvertently affect the results of an experiment, although they are not the variables of primary interest. These factors, if not controlled or accounted for,
can lead to inaccurate conclusions. In the context of the creatine supplement study, some potential extraneous variables included:

• The age of the participants
• Their weight
• Lean body mass
• Capacity to lift weights

The researchers managed these variables effectively by selecting participants who were similar in these aspects. This ensures that any changes in the response variable, which was the gain in fat-free mass, were more likely due to the creatine supplement rather than differences in participants' weight or age.
By controlling these extraneous variables, the study becomes more reliable, providing clearer insights into the impact of creatine supplementation.

Placebo Effect

The placebo effect refers to a phenomenon where individuals experience a perceived or actual improvement in their condition despite receiving a non-active treatment. This effect can result from participants' expectations of benefit, influencing their perceptions and behaviors.
In the study, to account for this,
researchers used a fake preparation for the control group. By doing this, they could ensure that any observed effects on muscle mass were due to the creatine supplement itself and not participants' beliefs or expectations.
This blinding approach minimizes the placebo effect, maintaining the integrity of the study's results by isolating the true effects of the treatment under investigation.

Double-blind Experiment

A double-blind experiment is a research strategy that prevents both participants and researchers from knowing who receives the treatment and who receives a placebo. This methodology reduces bias from both parties, leading to more objective and reliable results.
In the creatine supplement study, the researchers did not implement a double-blind design, which means they knew which participants were receiving creatine and which were given the placebo.
Researchers could inadvertently influence the outcomes, either in how they interact with participants or in the interpretation of results.

• This introduces the possibility of bias, affecting the study's credibility.
• A double-blind approach could have minimized such biases, leading to a more robust set of conclusions.

By adopting a double-blind design, the potential for unintentional influence would decrease, ensuring the observed effects stem mainly from the creatine treatment itself.

Response Variable

A response variable, sometimes referred to as a dependent variable, is the outcome that researchers aim to measure in an experiment to see the effects of the independent variable—the treatment being tested. In the creatine study, the response variable was the gain in fat-free mass expressed as a percentage.
This variable is crucial because it quantifies the effects of the creatine supplementation on the study participants.
By measuring changes in fat-free mass, researchers can determine if the creatine supplement actually contributes to muscle development.

• This measurement provides direct evidence of treatment effectiveness.
• It allows researchers to compare outcomes between the treatment and control groups.

Understanding the response variable is essential, as it ensures the correct evaluation of an experiment's success and reliability.