In scientific testing, a group of individuals or cases that receive the experimental treatment or factor. Experimental groups can be contrasted with control groups.

A scientific test that involves manipulating some factor or factors in a system in order to see how those changes affect the outcome or behavior of the system. Experiments are important in science, but they are not the only way to test scientific ideas. To learn more about the role of experiments in science, visit Tactics for testing ideas. To learn about experimental design, visit our side trip Designing fair tests.

In science, a potential outcome of a scientific test that is arrived at by logically reasoning about a particular scientific idea (i.e., what we would logically expect to observe if a given hypothesis or theory were true or false). The expectations generated by an idea are sometimes called its predictions. Observations that match the expectations generated by an idea are generally interpreted as supporting evidence. Mismatches are generally interpreted as contradictory evidence. To learn more about the relationship between expectations and observations, visit The core of science. To learn more about why this website uses the term expectation instead of prediction, visit our page on Misconceptions about science.

In reference to statistics, the difference between a computed or measured value and the true value. To learn more, visit our misconception on the topic of error.

Test results and/or observations that may either help support or help refute a scientific idea. In general, raw data are considered evidence only once they have been interpreted in a way that reflects on the accuracy of a scientific idea.