Experiments and Quasi-Experiments
|•||Threats to Internal Validity|
Quasi-experiments, and especially experiments, are attractive when researchers seek to address causal issues through research design. These designs establish values of an independent variable outside the control of the cases studied; a researcher or an exogenous event is responsible for levels of the independent variable. As a consequence, variation in the dependent variable cannot be responsible for variation in the independent variable. Causal influence, if it exists, must go from the independent to the dependent variable.