Question

The Institute of Psychiatry at Kings College London found that dealing with "infomania" has a temporary, but significant derogatory effect on IQ. (Discover, November 2005). In this experiment, researchers divided volunteers into two groups. Each subject took an IQ test. One group had to check email and respond to instant messages while taking the test while the second group took the test without any distraction. The distracted group had an average score that was 10 points lower than the average for the control group. Explain why it is important that the researchers created the two experimental groups in this study by using random assignment.

Short answer

Random assignment is critical in this experiment because it ensures the initial comparability of the groups. It eliminates the influence of confounding variables, thus any observed differences in IQ test scores between groups can confidently be attributed to the effect of 'infomania', not other personal characteristics or biases.

Step-by-step solution

Understand the purpose of random assignment

Random assignment is a method used in experimental design to allocate subjects randomly to different groups. In this case, individuals are randomly assigned to either the control group (no distractions during the test) or the experimental group (checking emails and responding to messages during the test). The purpose is to ensure each participant has an equal chance of being placed into any group. This eliminates the bias in group selection and makes the groups comparable.

Recognition of the effect of random assignment on the analysis

Since participants are assigned randomly, the groups' compositions are likely to be similar. As a result, observed differences in the outcomes (IQ test scores) are attributable to the experimental manipulation (presence or absence of distractions) and not due to differences in group characteristics. Thus, if a statistically significant difference in test scores is found, it can be inferred that the 'infomania' has an effect on IQ.

Summary of the importance of random assignment

The use of random assignment in this experiment is crucial as it allows researchers to confidently attribute any differences observed in IQ test scores to the experimental treatments. Without random assignment, it would be possible that some other characteristic of the students—not the variable the researchers are studying—caused the score difference.

Key concepts

Experimental Design

Creating an experiment that yields reliable and valid results involves careful planning, which is known as experimental design. A key component of this design is to control for variables that could influence the outcome of the experiment.

Why Is Experimental Design Important?

In the context of the infomania and IQ study, the researchers aimed to isolate the effect of distractions such as emails and instant messages on IQ scores. To ensure that any changes in IQ were due to the distractions — and not other factors — a robust experimental design was paramount.

• Controlled Environment: Conducting the test in a setting that controls for external variables can help isolate the impact of 'infomania'.
• Standardized Procedures: Ensuring that all subjects undergo the same test under the same conditions, unless they're in the treatment group, maintains the experiment's integrity.
• Reproducibility: A solid experimental design also means that the study can be replicated by other researchers to test the reliability of the findings.

Through meticulous experimental design, researchers can attribute changes in the dependent variable (IQ scores) directly to the independent variable (the presence or absence of distraction), providing validity to their conclusions.

Control Group

A control group serves as a baseline in an experiment, providing a comparison against the experimental group to measure the effect of the independent variable.

Role of the Control Group in the IQ Experiment

The control group was not subject to distractions, unlike the experimental group. This distinction is crucial for several reasons:

• Comparison: Without the control group's results, it would be unclear whether the caused the drop in IQ scores or if it was a normal score range for the population.
• Eliminate Alternative Explanations: A control group helps to rule out other factors as the cause of the observed effect, strengthening the conclusion.
• Measure Effect Size: By comparing the experimental group's score deviation with that of the control group, the magnitude of 'infomania''s impact on IQ can be evaluated.

As such, including a control group is critical to establishing a causal link between the experimental condition and the observed effect on IQ scores.

Infomania and IQ

'Infomania' refers to the obsession with checking emails, instant messaging, and the compulsive need to stay connected with information streams. This contemporary issue has raised concerns about its potential impact on cognitive functions, specifically IQ.

Assessing the Infomania Effect

The King's College London study addressed this by comparing IQ test scores under different conditions.

• Evidence of Cognitive Impact: The study's findings suggest that multitasking with information streams can negatively affect cognitive performance.
• Focus on Temporary Effects: The experiment examined the immediate, temporary effect on IQ, not the long-term implications.

By using a controlled experiment with random assignment, the researchers aimed to demonstrate a clear, statistically significant relationship between 'infomania' and a decrease in IQ scores.

Statistical Significance

Statistical significance is a mathematical measure to determine whether the observed difference between groups in an experiment is due to the effect being studied or merely by chance.

Determining Significance in the Experiment

The IQ experiment's conclusion hinged on whether the 10-point difference between the groups' average scores was statistically significant. Here's why that matters:

• Confidence in Results: A statistically significant result increases the confidence that 'infomania' truly impacts IQ.
• Exceeding Random Variation: Significance means that the probability of the score difference occurring by random chance is very low, typically below a predetermined threshold (often 5%).
• P-Value: The exact probability value, called a p-value, quantifies the likelihood that the result could occur under the null hypothesis, where no effect is assumed.

Statistical significance is vital in backing up the claim that the distractions indeed caused the lower IQ scores, as opposed to the difference simply being a random fluctuation.