= Causal Inference = '''Causal inference''' is an experimental design used to isolate causation and then make use of predictive statistics. <> ---- == Description == To study the impact of a '''treatment''' on an '''outcome''', all other variables must be held constant. If a relationship can be observed ''ceteris paribus'', then '''causation''' has been identified. ---- == Natural Experiments == A '''natural experiment''' or '''true causal experiment''' involves random assignment of a treatment such that the treatment and control groups are identical. Methods for causal inference are then applied. The unit of measurement in social science is almost always ''people''. It isn't possible to form groups of ''identical people''. As a result, causal inference is generally inapplicable. Instead, methods for '''statistical inference''' are applied. A tolerance for Type I error ''(false negatives)'' is set as a '''critical value'''. Experimental data is measured and, if the [[Statistics/TestStatistic|test statistic]] is greater than the critical value, the null hypothesis can be rejected. ---- == Quasi-Experiments == A '''quasi-experiment''' is distinguished by the assignment of treatment. When the assignment was not completely random, but differences are expected to be controllable, quasi-experimental methods are applied. ---- == Observational Studies == An '''observational study''' does not feature any real assignment to treatment. Instead, subjects self-assign a 'treatment' through their own decisions and behavior. There is no reason to expect treatment and control groups to be identical. There are non-redundant '''confounders''' which are related to the treatment and/or the outcome that must be controlled for. ---- CategoryRicottone