===== Evaluating causal claims =====
{{topic>external_invalidity internal_invalidity statistical_conclusion_validity reverse_causation group_threat selection time_threats maturation history attrition panel_mortality contamination +research_methods:video}}

===== Assignments =====

{{topic>external_invalidity internal_invalidity statistical_conclusion_validity reverse_causation group_threat selection time_threats maturation history attrition panel_mortality contamination +research_methods:assignment}}