Ex post facto is a quasi-experimental study design examining how an independent variable, present prior to the study in the participants, affects a dependent variable. A quasi- experimental study simply means participants are not randomly assigned. Historical method uses primary sources and other evidence, including the evidence of archaeology, to research and then to write histories in the form of accounts of the past. Descriptive research describes situations. They do not make accurate predictions, and they do not determine cause and effect. Experimental research is a quantitative research method conducted with a scientific approach, where a set of variables are kept constant while the other set of variables are being measured as the subject of experiment.