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Nonexperimental research is research that lacks manipulation of an independent variable and/or random assignment of participants to conditions. While the distinction between experimental and nonexperimental research is considered important, it does not mean that nonexperimental research is less important or inferior to experimental research (Price, Jhangiani & Chiang, 2015).

When to use nonexperimental research

Often it is not possible, feasible, and/or ethical to manipulate the independent variable, nor to randomly assign participants to conditions or to orders of conditions. In such cases, nonexperimental research is more appropriate and often necessary. Price, et al. (2015) provide the following examples that demonstrate when the research question is better answered with non-experimental methods:

1. The research question or hypothesis contains a single variable rather than a statistical relationship between two variables (e.g., How accurate are people’s first impressions?).
2. The research question involves a non-causal statistical relationship between variables (e.g., is there a correlation between verbal intelligence and mathematical intelligence?).
3. The research question involves a causal relationship, but the independent variable cannot be manipulated, or participants cannot be randomly assigned to conditions or orders of conditions (e.g., Does damage to a person’s hippocampus impair the formation of long-term memory traces?).
4. The research question is broad and exploratory, or explores a particular experience (e.g., what is it like to be a working mother diagnosed with depression?).

As demonstrated above, it is the nature of the research question that guides the choice between experimental and non-experimental approaches. However, this is not to suggest that a research project cannot contain elements of both an experiment and a non-experiment. For example, nonexperimental studies that establish a relationship between two variables can be explored further in an experimental study to confirm or refute the causal nature of the relationship (Price, Jhangiani & Chiang, 2015).

Types of nonexperimental research

In social sciences it is often the case that a true experimental approach is inappropriate and unethical. For example, conducting a true experiment may require the researcher to deny needed treatment to a patient, which is clearly an ethical issue. Furthermore, it might not be equitable or ethical to provide a large financial or other reward to members of an experimental group, as can occur in a true experiment.

There are three types of non-experimental research: cross-sectional, correlational, and observational. In the following sections we explore each of three types of nonexperimental research.