Ex-Post Facto Research measures the cause-and effect relationship without manipulating the independent variables. While the experimental research starts from manipulating and controlling the independent variables and proceeds to observing the effect on the dependent variables, the Ex-Post Facto Research starts from identifying the existing conditions and proceeds to finding the cause of the conditions. If we observe that the students in a language department are dominated by female students, then we may conduct an Ex-Post Facto Research to find out whether sex influences the choice of students into language department. If we observe that most of the freshmen of the English Department graduating from ordinary Senior High School achieve English skills better than those graduating from state senior High Schools, then we may not to conduct an Ex-Post Facto Research to find out whether different High School background and the students affect students’ achievement in learning English skills.
Causal Comparative Research is the other name of Ex-Post Facto Research. Its involving both continuous as well as discrete variables for the independent variables that have (1) inherent characteristics (organismic) e.g., gender, ethnicity, personality traits (2) characteristics that should not be manipulated for ethical reasons, e.g. illegal drug use, cigarette smoking, or alcohol consumption, (3) characteristics that could be manipulated but that are not, e.g., school placement, social promotion to the next grade, or participant in psycho-therapy (Martens, D.M. 2010: 151)
With discrete variables, Causal Comparative research design can be used to investigate the different academic achievements between male and female students (independent sex variable), between Sundanese and Europe students (independent ethnicity variable), between moslem male students and non moslem male students (independent religion variable), between students whose parents are wiraswasta and those whose parents are not wiraswasta (independent parents’ profession variables)
With Continuous variables, Causal comparative research can be used to investigate the different academic achievement between students with high intelligence and low intelligence, between students from high socioeconomic status background and low socioeconomic status background, between students whose parents are Sarjana graduates and those whose parents are not school graduates.
Although the conclusions in Ex-Post Facto research or Causal Comparative Research show significant differences in the level of dependent variables (i.e. a group of students with high self-esteem achieve significantly higher in their academic achievement than those with low self-esteem, a group of students whose parents are wiraswasta perform significantly higher in their academic achievement than those whose parents are not wiraswasta, a group of freshmen of the English Department graduating from ordinary senior high schools achieve significantly higher level of English mastery at the end of their first semester English Application Program than those graduating from state senior high schools), since the research does not involve experimental manipulation of treatment independent variables, the significant differences in the level of dependent variables do not show confident proof of a cause-and-effect relationship (Martens, D.M. 2010:151).
Research Problems and Research Objective in Experimental Research
The following are examples of research problems and research objectives in experimental research.
Research Problem: Do senior junior high school students learning speaking skill in language lab better than those students learning speaking skill in conventional classroom?
Research Objective: This study tries to investigate the effectiveness of the use of language lab in increasing the students’ speaking skill.
Research Problem: Do Bilingual class in SDIT Al-Azhar Kediri learning Vocabulary skill achieve better than those students learning vocabulary on Regular class?
Research Objective: This study tries to measure the effectiveness of the use of bilingual class in increasing vocabulary mastery.
Ok, well. That’s the explanation of Ex-Post Facto Research. This is kinds of experimental research. Understanding each characteristics of experimental research is the important thing to do the Causal Comparative research in order to the goal of research can be achieved.