In psychology, an effect refers to the influence that one variable has on another. In psychological research, an effect is typically measured by comparing the outcomes of two or more groups that are different in some way, with one group serving as a control group and the other(s) as an experimental group.
For example, if a researcher is studying the effect of a new learning strategy on students' test scores, they might compare the test scores of a group of students who use the new strategy to those of a group of students who do not. The difference in test scores between the two groups could be considered the effect of the learning strategy on test scores.
Psychologists often use statistical tests to determine whether an observed effect is statistically significant, which means that it is unlikely to have occurred by chance and is therefore likely to be a true effect.
Understanding the effects of different variables on behavior and cognition is an important part of psychological research, as it can help to identify factors that influence people's thoughts, feelings, and actions and can inform the development of interventions and treatments.