Ways to control confounding variables so they do not affect the results of your experiment include:
Adjustment: Adjust study parameters to account for the confounding variable and minimize its effects.
Matching: Compare study groups with the same degree of confounding variables.
Multivariate analysis: Use when analyzing multiple variables at once.
Randomization: Spread confounding variables evenly between study groups.
Restriction: Remove subjects or samples that have confounding factors.
Stratification: Create study subgroups in which the confounding variable does not vary or vary much.