Random assignment means that every participant has the same chance of being chosen for the experimental or control group. It involves using procedures that rely on chance to assign participants to groups. Doing this means that every participant in a study has an equal opportunity to be assigned to any group.
For example, in a psychology experiment, participants might be assigned to either a control or experimental group. Some experiments might only have one experimental group, while others may have several treatment variations.
Using random assignment means that each participant has the same chance of being assigned to any of these groups.
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So what type of procedures might psychologists utilize for random assignment? Strategies can include:
A psychology experiment aims to determine if changes in one variable lead to changes in another variable. Researchers will first begin by coming up with a hypothesis. Once researchers have an idea of what they think they might find in a population, they will come up with an experimental design and then recruit participants for their study.
Once they have a pool of participants representative of the population they are interested in looking at, they will randomly assign the participants to their groups.
By using random assignment, the researchers make it more likely that the groups are equal at the start of the experiment. Since the groups are the same on other variables, it can be assumed that any changes that occur are the result of varying the independent variables.
After a treatment has been administered, the researchers will then collect data in order to determine if the independent variable had any impact on the dependent variable.
It is important to remember that random assignment is not the same thing as random selection, also known as random sampling.
Random selection instead involves how people are chosen to be in a study. Using random selection, every member of a population stands an equal chance of being chosen for a study or experiment.
So random sampling affects how participants are chosen for a study, while random assignment affects how participants are then assigned to groups.
Imagine that a psychology researcher is conducting an experiment to determine if getting adequate sleep the night before an exam results in better test scores.
They hypothesize that participants who get 8 hours of sleep will do better on a math exam than participants who only get 4 hours of sleep.
The researcher starts by obtaining a pool of participants. They find 100 participants from a local university. Half of the participants are female, and half are male.
The researcher then assigns random numbers to each participant and uses a random number generator to randomly assign each number to either the 4-hour or 8-hour sleep groups.
Those in the 8-hour sleep group agree to sleep for 8 hours that night, while those in the 4-hour group agree to wake up after only 4 hours. The following day, all of the participants meet in a classroom.
Everyone takes the same math test. The test scores are then compared to see if the amount of sleep the night before had any impact on test scores.
Random assignment is important in psychology research because it helps improve a study’s internal validity. This means that the researchers are sure that the study demonstrates a cause-and-effect relationship between an independent and dependent variable.
Random assignment improves the internal validity by minimizing the risk that there are systematic differences in the participants who are in each group.
Posted on Published: September 14, 2017 - Last updated: January 25, 2024
