Which of the following is a key characteristic of an experiment?

A key characteristic of an experiment is random assignment. This process involves randomly assigning participants to different treatment groups to ensure that each group is as similar as possible at the start of the experiment. This helps eliminate bias and allows researchers to isolate the effect of the treatment or intervention being studied. Random assignment helps ensure that any differences observed in the outcomes can be attributed to the treatments rather than other confounding variables.

In contrast, an observational study collects data without manipulating conditions or assigning treatments, which is why it does not have the same level of control over variable variables. Survey distribution refers to the methods used to collect data from a sample, but it does not involve the manipulation of independent variables. Qualitative data collection focuses on gathering non-numeric information, which is not inherently experimental. Thus, among the provided options, random assignment is the fundamental characteristic that distinguishes experiments from other types of studies.