AP Psychology Practice Test

Random assignment is a fundamental aspect of experimental research that involves assigning participants to different conditions or groups purely by chance. This process helps ensure that each participant has an equal opportunity to be placed in any group, which minimizes the impact of pre-existing differences among participants. By doing so, it enhances the internal validity of an experiment, as it helps to ensure that any effects observed can be attributed to the independent variable being tested rather than individual differences between participants. Other concepts, such as determining the placebo effect, selecting dependent variables, or allowing participants to choose their conditions, do not align with the core definition of random assignment. These processes do not employ chance in the same way and can introduce biases or confounding variables that random assignment seeks to eliminate.