Question

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

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

Preparing the Labels

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

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.

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.

Key concepts

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—in 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.