Types of Studies in Psychological Research

There are three main types of studies in psychological research: descriptive, correlational, and experimental. In descriptive and correlational designs, researchers examine behavior as it naturally occurs. These types of studies are useful for describing and predicting behavior, but they do not allow researchers to assess causality. Correlational designs have limitations, including directionality problems (knowing whether variable A caused B or the reverse) and the third variable problem, (the possibility that a third variable is responsible for variables A and B). In an experiment, a researcher manipulates the independent variable to study how it affects the dependent variable. An experiment allows a researcher to establish a causal relationship between the independent and dependent variable and to avoid the directionality problem when trying to understand how one variable might affect another. An experiment gives the researcher the greatest control, so that the only thing that changes is the independent variable. If the goals is to conclude that changes in one variable caused changes in another variable, the researcher must assign participants at random to different groups to make the groups as equal as possible (on average) on all variables except the one being studied. The researcher wants to know about a population, but because it is usually impossible for everyone in the population to be a research participant, the researcher uses a representative sample of the population and then generalizes the findings to the population. Random sampling, in which everyone in the population has an equal chance of being a research participant, is the best way to sample, but since this is usually not possible, most researchers use a convenience sample. Among the most important factors in whether the results from a particular sample can be generalized back to the population is sample size. In general, large samples provide more accurate results than small ones.