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The following is from an article titled "After the Workout, Got Chocolate Milk?" that appeared in the Chicago Tribune (January 18,2005\():\) Researchers at Indiana University at Bloomington have found that chocolate milk effectively helps athletes recover from an intense workout. They had nine cyclists bike, rest four hours, then bike again, three separate times. After each workout, the cyclists downed chocolate milk or energy drinks Gatorade or Endurox (two to three glasses per hour); then, in the second workout of each set, they cycled to exhaustion. When they drank chocolate milk, the amount of time they could cycle until they were exhausted was similar to when they drank Gatorade and longer than when they drank Endurox. For the experiment to have been well designed, it must have incorporated random assignment. Briefly explain where the researcher would have needed to use random assignment for the conclusion of the experiment to be valid.

Short Answer

Expert verified
The researcher would have needed to use random assignment when determining which drink (chocolate milk, Gatorade, or Endurox) the cyclists received after their first workout. By randomly allocating the post-workout drinks among the participants, potential biases and confounding variables would have been adequately controlled.

Step by step solution

01

Understanding the Concept

The important factor at play here is random assignment. In scientific experiments, random assignment is a technique that randomly allocates subjects into different groups to ensure each test subject has an equal chance of being assigned to any of the groups. This is done to prevent bias or confounding variables from skewing results.
02

Applying the Concept to the Scenario

In the given scenario of the cycling study, the point at which random assignment applied would have been when determining which post-workout drink (chocolate milk, Gatorade, or Endurox) the cyclists received after their first workout. The researchers did not randomly assign the participants to different drinks, but the experiment's conclusions would have been more valid if they had. If it was not random, there could be a pattern or bias in which participants received which drinks, which could impact the result of the experiment.
03

Conclusion

Understanding and using random assignment is essential in experimental design to avoid biases and confounding variables. By randomly assigning the different beverages to the cyclists in the experiment, the researcher would have controlled for other variables that could influence the results, making the experiment’s conclusions more valid.

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Key Concepts

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

Scientific Experiments
Scientific experiments are a cornerstone of understanding phenomena in the natural world. They allow researchers to test hypotheses in a controlled environment and determine the effects of specific variables. In the case described in the Chicago Tribune article, scientists conducted an experiment to assess the efficacy of chocolate milk compared to other energy drinks in helping athletes recover from intense workouts. An essential aspect of this kind of research is ensuring the experiment is valid and reliable. Validity means the experiment measures what it is supposed to measure; reliability refers to the consistency of the results over repeated trials. By carefully planning an experiment with a clear independent variable (the drink given) and a well-defined dependent variable (time to exhaustion), researchers aim to establish a cause-and-effect relationship.

To achieve this, rigorous methodological standards must be adhered to, which include controlling external factors that could influence the outcome and being meticulous in data collection and analysis. This ensures that the conclusions drawn from the experiment truly reflect the effects of the variable being tested, rather than some other extraneous factor. In educational contexts, understanding the framework of scientific experiments helps students grasp how we acquire new knowledge and why certain procedures, like random assignment, are essential.
Experimental Design
Well-executed experimental design is a blueprint for robust scientific inquiry. It involves a series of decisions that outline how an experiment will be conducted to test a specific hypothesis. Each choice in the design process influences the experiment's overall quality. For the cycling study, the experimental design includes determining the sample size, selecting appropriate control and experimental groups, and deciding on the treatments (in this case, drinks) to administer. The aim of experimental design is to eliminate or control external variables that might confound the results.

An integral feature of many experimental designs is random assignment, which is crucial in maintaining the validity of the experiment. By randomly assigning subjects or units to different treatments, researchers ensure that each group is statistically equivalent at the start of the experiment. This randomness helps prevent selection bias, meaning the results are less likely to be affected by unknown or unmeasured factors. For educators and students, appreciating the intricacies of experimental design is vital for both conducting research and critically evaluating the research of others.
Bias and Confounding Variables
Bias and confounding variables are two significant concerns in experimental research that can compromise the integrity of the results. Bias refers to systematic errors that can be introduced into sampling or testing processes, leading to results that deviate from the truth systematically. Confounding variables, on the other hand, are extraneous variables that the researcher failed to control or eliminate, which could cause a false association between the studied variables.

In the chocolate milk experiment, potential biases could arise if, for example, the cyclists who received chocolate milk were already better performers, or if they had different recovery practices. Confounding variables might include the overall diet, hydration level, or rest quality of the cyclists, which could independently affect their performance. The exercise improvement advice focuses on the value of random assignment as a tool to reduce these risks. By ensuring that each treatment group is comparable in all respects except the experimental intervention, the influence of bias and confounding variables on the study's outcome is minimized. Consequently, students must learn to identify and adjust for potential biases and confounders, thereby enhancing the credibility of their experimental findings.

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Most popular questions from this chapter

Whether or not to continue a Mardi Gras Parade through downtown San Luis Obispo, California, is a hotly debated topic. The parade is popular with students and many residents, but some celebrations have led to complaints and a call to eliminate the parade. The local newspaper conducted online and telephone surveys of its readers and was surprised by the results. The online survey received more than 400 responses, with more than \(60 \%\) favoring continuing the parade, while the telephone response line received more than 120 calls, with more than \(90 \%\) favoring banning the parade (San Luis Obispo Tribune, March 3,2004 ). What factors may have contributed to these very different results?

According to the article "Effect of Preparation Methods on Total Fat Content, Moisture Content, and Sensory Characteristics of Breaded Chicken Nuggets and Beef Steak Fingers" (Family and Consumer Sciences Research Journal [1999]: 18-27), sensory tests were conducted using 40 college student volunteers at Texas Women's University. Give three reasons, other than the relatively small sample size, why it would not be a good idea to generalize any study results to the population of all college students.

Do ethnic group and gender influence the type of care that a heart patient receives? The following passage is from the article "Heart Care Reflects Race and Sex, Not Symptoms" (USA Today, February 25,1999\():\) Previous research suggested blacks and women were less likely than whites and men to get cardiac catheterization or coronary bypass surgery for chest pain or a heart attack. Scientists blamed differences in illness severity, insurance coverage, patient preference, and health care access. The researchers eliminated those differences by videotaping actors-two black men, two black women, two white men, and two white women - describing chest pain from identical scripts. They wore identical gowns, used identical gestures, and were taped from the same position. Researchers asked 720 primary care doctors at meetings of the American College of Physicians or the American Academy of Family Physicians to watch a tape and recommend care. The doctors thought the study focused on clinical decision making. Which video a particular doctor watched was determined by the roll of a four- sided die. Answer the following seven questions for the described experiment. (Hint: Reviewing Examples 1.5 and 1.6 might be helpful.) 1\. What question is the experiment trying to answer? 2\. What are the experimental conditions (treatments) for this experiment? 3\. What is the response variable? 4\. What are the experimental units, and how were they selected? 5\. Does the design incorporate random assignment of experimental units to the different experimental conditions? If not, are there potentially confounding variables that would make it difficult to draw conclusions based on data from the experiment? 6\. Does the experiment incorporate a control group and/or a placebo group? If not, would the experiment be improved by including them? 7\. Does the experiment involve blinding? If not, would the experiment be improved by making it single- or doubleblind?

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. In a study of whether taking a garlic supplement reduces the risk of getting a cold, 146 participants were assigned to either a garlic supplement group or to a group that did not take a garlic supplement ("Garlic for the Common Cold," Cochrane Database of Systematic Reviews, 2009). Based on the study, it was concluded that the proportion of people taking a garlic supplement who get a cold is lower than the proportion of those not taking a garlic supplement who get a cold.

A study described in Food Network Magazine (January 2012) concluded that people who push a shopping cart at a grocery store are less likely to purchase junk food than those who use a hand-held basket. a. Do you think this study was an observational study or an experiment? b. Is it reasonable to conclude that pushing a shopping cart causes people to be less likely to purchase junk food? Explain why or why not.

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