The Experimental Study Design in Research

The experimental study design has many different approaches to carry on and to understand each of these designs one needs to study them in detail. The experimental study design is based on the scientific approach to collect data and it uses naturalistic paradigm in research. Its use is more common in natural and pure sciences where quantitative research is the appropriate approach to finding facts.  In social sciences as well as psychology the experimental study design can be classified into the following:

The post-test only design

As the name suggests in the post-test only design or the after-only design the investigator studies the impact of an intervention on the target population. In this type of design, the investigator does not pre-test the audience in order to get information. To compare the results of the intervention with that before the intervention the investigator either asks the respondents questions or he uses existing data. Where the adequate amount of data is available about the pre-test situation the investigator can securely use this type of design in his research.


  • It takes less time to conduct this type of experimental design because there is no need to do the pre-test.
  • In real life, there are situations where the investigator has no other options but to apply the intervention and see the results and he has no time to do the pre-test evaluations.


  • Technically it’s a faulty design because the two sets of data are not comparable each is taken under different circumstances. The investigator has no control over the extraneous factors that might have impacted the pretest data.
  • It studies the net impact and different variables that might impact the situation cannot be segregated from the situation.

The pretest-post-test design

This type of experimental design tests the audience before the intervention and after the intervention. It has the benefit that the two sets of data are comparable to each other and the purpose is to fully understand the impact of the program on the audience.


  • The pretest-post-design has a comparable data that is otherwise impossible in the post-test design.


  • The disadvantage of this design is that it does not have control over extraneous factors that might impact the situation.

The control design

In control design, the investigator applies the intervention on two groups: one is called as the experimental group, and the other is called as the control group. The sample is randomly selected and they are randomly assigned to both the control group and the experimental group. It is also called as the true experiment because the investigator has full control on the extraneous factors and studies only the impact of the independent variable on the dependent variable. The experimental group recieves hte intervention while the control group is deprived of that treatment to know the impact.


  • The biggest benefit of the control design is that the investigator has a control over the extraneous variables that might impact the situation.
  • It also has the benefits of pre-test and post-test design along with the control group.
  • The investigator can fully understand the impact of the intervention.
  • This increases the reliability of the research tool as the extraneous factors are kept under control of the investigator.
  • The subjects are randomly assigned to the control group or the experimental group hence the chances of systematic bias is avoided.

The comparative design

In the comparative study design, the investigator compares the impact of different treatments on the audience. The investigator can study the impact of as many treatments or programs as he wants to. He divides the population into as many groups as many are the programs or the treatments that he wants to study and compare. On each group, he applies different treatments and he studies each group before the treatment and after the treatment. The results of each group are then compared to make some evaluations of different treatments.  It has all the benefits of pretest-post-test design as well as all the benefits of a control design.



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