Final answer:
Random assignment is a method used in experimental design to create equal groups at the start of an experiment and ensure that everyone in the population has an equal chance of being included in the study. the correct answer is a.
Step-by-step explanation:
Random assignment is a method used in experimental design to create equal groups at the start of an experiment. It ensures that everyone in the population has an equal chance of being included in the study. By randomly assigning participants to different groups, any preexisting differences between the groups can be minimized, allowing us to attribute any differences observed between the groups to the manipulation of the independent variable.
The purpose of random assignment in experimental research is to create equal groups at the beginning of an experiment, ensuring that any observed differences in outcomes are attributable to the manipulation of the independent variable, rather than preexisting differences between the groups.
This process helps to eliminate the influence of lurking variables, meaning factors not controlled in the experiment that could affect the results. Therefore, the correct answer is a) create equal groups at the start of an experiment.