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Chapter 1: Problem 33

A study of college students showed a temporary gain of up to nine IQ points after listening to a Mozart piano sonata. This result, dubbed the Mozart effect, has since been criticized by a number of researchers who have been unable to confirm the result in similar studies. Suppose that you want to determine if there is really is a Mozart effect. You decide to carry out an experiment with three experimental groups. One group will listen to a Mozart piano sonata that lasts 24 minutes. The second group will listen to popular music for the same length of time, and the third group will relax for 24 minutes with no music playing. You will measure IQ before and after the 24 minute period. Suppose that you have 45 volunteers who have agreed to participate in the experiment. Describe a method of randomly assigning each of the volunteers to one of the experimental groups.

Short Answer

Expert verified
Assign numbers 1-45 to all volunteers. Shuffle these labels thoroughly and draw 15 labels for the Mozart sonata group, another 15 for the popular music group, and the remaining 15 for the quiet relaxation group. Each draw is performed without replacement to maintain randomness.

Step by step solution

01

Preparing the Labels

Prepare labels representing all the volunteers. This can be accomplished by numbering from 1 to 45.
02

Shuffle the Labels

To ensure randomness, shuffle all the labels. This can be done by placing all the labels in a container and then stirring them around.
03

Divide the Volunteers into Groups

Draw out 15 labels, one by one, without returning any back to the container each time. The first 15 are assigned to the Mozart sonata group. Repeat the draw for the next 15 labels assigning them to the popular music group, and the final 15 labels form the quiet relaxation group. Ensure no bias is introduced during this process by maintaining a blind draw.

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Key Concepts

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

Random Assignment in Experiments
When conducting experiments, it's crucial to eliminate as much bias as possible to ensure the results are reliable. Random assignment is a technique used to allocate participants to different groups in an unbiased manner. This means that every volunteer has an equal chance of being placed in any of the groups.

For example, in an experiment designed to test the Mozart effect, you would label 45 volunteers and then randomly draw their labels to assign them to the Mozart sonata group, the popular music group, or the quiet relaxation group. By shuffling the labels thoroughly, random assignment minimizes confounding variables and helps to isolate the variable being tested鈥攊n this case, the type of audio exposure and its effect on IQ.
Experimental Design
A well-thought-out experimental design forms the backbone of any reliable study. It specifies how participants are selected, assigned to groups, and how the experiment is carried out. A good design ensures that the conclusions drawn are a direct result of the variable being tested, rather than external factors.

In the Mozart effect experiment, the design includes the type of music or relaxation method and the before-and-after IQ measurements. A solid design will address potential biases and incorporate elements like blinding and randomization to protect the integrity of the results.
Control Groups
Including control groups is a fundamental aspect of experimental design. Control groups enable researchers to compare results between the experimental group and a baseline or standard condition. In the context of the Mozart effect experiment, the control group could be the participants who relax without music. This group helps determine if changes in IQ scores are due to the specific conditions of the experiment (listening to Mozart or popular music) or if they are influenced by other factors like relaxation.

Without this comparison, it's difficult to attribute changes in IQ scores to the music alone, as other aspects of the experimental environment could be responsible. The control group, therefore, acts as a pivotal reference point for interpreting the effectiveness of the experimental conditions.
IQ Measurement
In experiments like these, IQ measurement is often the dependent variable used to assess cognitive ability. IQ tests aim to provide a standardized way to compare intelligence levels across different individuals. Usually, these tests assess various aspects like logic, math, language, and spatial reasoning.

For the Mozart effect, the difference in IQ scores before and after the experiment is particularly important. To ensure accurate measurements, a reliable and validated IQ test must be used, and conditions should be kept consistent to prevent external factors from affecting the outcome. It should be noted that IQ is a complex and sometimes controversial measure, influenced by many factors and not entirely definitive of a person's cognitive ability.

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Most popular questions from this chapter

In many digital environments, users are allowed to choose how they are represented visually online. Does the way in which people are represented online affect online behavior? This question was examined by the authors of the paper "The Proteus Effect: The Effect of Transformed Self-Representation on Behavior" (Human Communication Research [2007]: 271-290). Participants were randomly assigned either an attractive avatar (a graphical image that represents a person) to represent them or an unattractive avatar. The researchers concluded that when interacting with a person of the opposite gender in an online virtual environment, those assigned an attractive avatar moved significantly closer to the other person than those who had been assigned an unattractive avatar. This difference was attributed to the attractiveness of the avatar. Explain why the researchers would not have been able to reach this conclusion if participants had been allowed to choose one of the two avatars (attractive, unattractive) themselves.

Use the following information to answer. The paper "Turning to Learn: Screen Orientation and Reasoning from Small Devices" (Computers in Human Behavior [2011]: \(793-797\) ) describes a study that investigated whether cell phones with small screens are useful for gathering information. The researchers wondered if the ability to reason using information read on a small screen was affected by the screen orientation. The researchers assigned 33 undergraduate students who were enrolled in a psychology course at a large public university to one of two groups at random. One group read material that was displayed on a small screen in portrait orientation, and the other group read material on the same size screen but turned to display the information in landscape orientation (see the following figure). Did the study use random assignment to experimental groups?

The article "Super Bowls: Serving Bowl Size and Food Consumption" (Journal of the American Medical Association [2005]: 1727-1728) describes an experiment investigating how the size of serving bowls influences the amount a person eats. In this experiment, graduate students at a university were recruited to attend a Super Bowl party. The paper states that as the students arrived, they were "led in an alternating order to one of two identical buffet tables on opposite sides of an adjoining room. The tables had identical amounts of snacks, such as nuts, pretzels, and chips. All of the snacks contained approximately the same number of calories per gram. On one of the tables the snacks were set out in large serving bowls and on the second table the snacks were set out in smaller serving bowls. The students were given a plate and invited to serve themselves before going to another room to watch the game. When they arrived at the game room, their plates were weighed and the number of calories in the food on the plate was estimated." The researchers concluded that serving bowl size does make a difference, with those using large serving bowls tending to take more food. a. Do you think that the alternate assignment to the experimental groups (large serving bowls, small serving bowls) based on arrival time is "close enough" to random assignment? That is, do you think it would tend to create comparable experimental groups? b. In this study, the research assistant who weighed the plates and estimated the calorie content of the food on the plate was blinded as to which experimental group the plate belonged to and was also blinded as to the purpose of the experiment. Why do you think the researchers chose to incorporate this type of blinding?

A petition with 500 signatures is submitted to a college's student council. The council president would like to determine what proportion of those who signed the petition are actually registered students at the college. There is not enough time to check all 500 names with the registrar, so the council president decides to select a simple random sample of 30 signatures. Describe how she might do this.

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?
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