Hi Marcus,
I think your examples are close, but want to make sure the difference is clear. In a post-only experiment, a researcher may examine shopper satisfaction by giving a satisfaction survey to customers as they checkout in-store or online. In a pre- and post-test design, a store may ask about satisfaction as a shop enters the store in-person or virtually, and then ask again after checkout.
Posttest only and Pretest-posttest design with examples Posttest-only control group design is a type of research design in which there are two groups. One group will receive the treatment, and there will be another group who won't receive the treatment (Frey, 2018). For example, if a posttest-only design is conducted among two groups in which one group has purchased food online, the other group has not purchased food from any online site. In this context, opinions from the people who have purchased food online will be taken and measure from the group of people who have not purchased food online yet. A pretest-posttest design is an experimental design where measurement is taken after and before the treatment process. For example, suppose the same scenario is taken as above, then in the pretest-posttest format. In that case, a researcher can compare the pre-treatment and post-treatment results among people whether people who have purchased food online had the same perception as those who still have not bought food online or cannot be measured through a pretest-posttest design. Pretest-posttest design helps a researcher to identify the difference between the experimental and control group. Only measuring the difference, the pretest-posttest design also allows a researcher the degree of change, growth, or decline in the outcome among the participant's experience. The pretest-posttest design also helps the researcher determine the trend through a series of treatments; in the pretest-posttest researcher, the researcher can compare two pretest and posttest groups the outcome in a random process (Baldwin, 2018). Posttest-only design segregates the population or ensures internal control. Work from the pretest-posttest design cannot be generalized because there are some of the rules on population. Significant threats of posttest-only design Despite ensuring a high degree of internal validity, the Posttest-only design is applicable when there are two groups. At the same time, we can apply the pretest-posttest method to a single group. The process of each design brings certain limitations in the conclusion drawing process. Posttest only analyzes the factors after treatment but pretest-posttest design capable enough to compare before and after experiments. Hence, the pretest-posttest design offers a realistic conclusion than the posttest only formatting. Importance of Random assignment Random assignment is an experiment over random groups. Random assignment is helpful because it ensures members of each group equally. Moreover, the approach is more effective when the population is large. In choosing a lottery game-winner, this random assignment approach is used because of a broader audience. Advantages and disadvantages of independent group design over repeated measures Independent group design is a less time-consuming process because the researcher is not required to conduct the test before the treatment process. Moreover, the cost of independent group design is comparatively less. Achieving objectives becomes easier in independent group design. On the other hand, independent group design sometimes led to different results as opinion from diverse groups is considered (Curtis et al. 2015). While repeated measures always ensure stability in the outcome. While looking into the benefits of repeated measurements over independent group design, repeated measures provide higher statistical power than independent group design. Repeated measure design also helps the researcher to predict the effect of the future. References: Baldwin, L. (2018). Research Designs and Their Limitations. In Research Concepts for the Practitioner of Educational Leadership (pp. 37-48). Brill Sense. Curtis, M. J., Bond, R. A., Spina, D., Ahluwalia, A., Alexander, S. P., Giembycz, M. A., ... & McGrath, J. C. (2015). Experimental design and analysis and their reporting: new guidance for publication in BJP. Frey, B. (2018). The SAGE encyclopedia of educational research, measurement, and evaluation (Vols. 1-4). Thousand Oaks, CA: SAGE Publications, Inc.