1. Experimental design refers to how experiments are structured in order to ensure validity and reliability of results. 2. There are several types of experimental designs including true experimental, quasi-experimental, pre-experimental, ex post facto, and factorial designs. 3. True experimental designs use random assignment and control/experimental groups to establish causation. Quasi-experimental designs lack random assignment so can only suggest relationships between variables. Ex post facto designs study pre-existing groups and cannot prove causation. Factorial designs study effects of multiple independent variables.