Given Hapunda

98 2. Pretest-Posttest Comparison-Group Design This design is also referred to as the non-equivalent comparison group design (Rubin & Babbie, 2013). It is also a type of quasi-experimental design with a non-random assignment to the control group. So, there is no equivalence between the groups. This design permits data to be collected before and after the intervention. It is a combination of the static-group comparison design and the one-group pretest- posttest design. As such, it controls for all past learning, thereby identifying some differences and similarities between the two groups. Advantages of the Pretest-Posttest Comparison-Group Design With this design, the comparison group is used to address history or prior exposure to other stimulus or intervention. More so, the pre-test identifies to some extent the differences and similarities between the groups. Disadvantages of Pretest-Posttest Comparison-Group Design In this design, selection and maturation interaction are a potential threat to internal validity. For instance, the pre-test may indicate that the group that received the training programme had more knowledge about contraceptives than the comparison group prior to the intervention. If the post-test also indicates this difference between the intervention and comparison groups, then maturation could be the possible cause for this difference. This problem with internal validity is usually as a result of lack of random assignment of subjects to the comparison group. With regard to threats to external validity, selection- treatment interaction is a major problem which can in turn affect generalisation and replication of the results. This is mainly due to lack of randomisation. Additionally, repetitive exposure to the same material, be it in the past or during training may be a threat to external validity (Marlow, 2011). Figure 5: Pretest-Posttest Comparison-Group Design Pre-test Programme /intervention Post-test Pre-test Control group Post-test