- Stratification can be used to ensure that subgroups of participants are randomly assigned to each experimental condition. Gender, age, and other demographic data may be used to accomplish this. Stratification can be used to eliminate confounding variables (variables not studied by the researcher), making it easier to find and evaluate correlations between variables in the study. - For example, in a fitness research wherein age and gender were believed to impact the outcomes, the confounding variable may be used to divide participants into groups. One drawback of this strategy is that it necessitates knowledge of the factors that must be controlled.