CDIP Domain 5: Research & Education Practice Test

Internal validity is about ensuring that observed effects are caused by the treatment, not by other influences. Confounding, selection bias, and maturation are classic threats because they can create differences between groups or over time that mimic or hide the true effect of the intervention.

Confounding happens when an outside factor is related to both the treatment and the outcome, making it unclear what caused the result. Selection bias arises when the way participants are assigned or selected leads to groups that differ in important ways before the intervention. Maturation refers to natural changes within participants over time that could affect the outcome independent of the treatment.

Randomization is a strategy to guard against these threats. By randomly assigning participants to groups, you distribution both known and unknown characteristics evenly, so preexisting differences are less likely to skew results. This helps ensure that any observed post-treatment differences are more likely due to the treatment itself rather than confounding factors, selection biases, or time-related changes. So randomization is not a threat to internal validity; it strengthens it.