What is the difference between experimental and ex post facto research designs?
http://researchunesa.blogspot.com/2010/03/experimental-ex-post-facto-research.html
The difference between experimental and ex post facto research designs lies in the way participants are assigned to groups and the level of control the researcher has over the variables being studied.
Experimental research design involves manipulating an independent variable and observing the effects on a dependent variable. Participants are randomly assigned to different groups: the experimental group, which receives the treatment or intervention, and the control group, which does not. By randomly assigning participants, researchers can assume that any differences observed between the groups are due to the manipulation of the independent variable.
To conduct experimental research, researchers typically follow these steps:
1. Identify the research question and hypothesis.
2. Select the variables to manipulate and measure.
3. Randomly assign participants to groups.
4. Administer the treatment or intervention to the experimental group.
5. Collect data on the dependent variable from both groups.
6. Analyze the data using statistical techniques to determine if there are significant differences between the groups.
On the other hand, ex post facto research designs (also known as observational or quasi-experimental designs) do not involve random assignment. Instead, researchers observe and compare groups that are already formed based on existing characteristics or conditions. In ex post facto research, the independent variable has already occurred naturally, and the researcher cannot actively manipulate or control it.
Here are the steps typically followed in an ex post facto research design:
1. Identify the research question and hypothesis.
2. Select the dependent variable to measure.
3. Identify existing groups or conditions that differ naturally in the independent variable.
4. Collect data on the dependent variable from these groups or conditions.
5. Analyze the data using statistical techniques to determine if there are significant differences between the groups.
Ex post facto research is often used when it is not possible or ethical to manipulate variables in an experimental setting. However, because the researcher has less control over confounding variables in ex post facto designs, it is generally considered less rigorous than experimental research.