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91 Disadvantages of Experimental Designs Experimental designs are not always feasible or practical since they are not easy to set up and execute as they require random assignment of subjects to groups (experimental and control groups). More so, experimental designs are not easy to conduct in the natural setting or environment, such as school or church since it may be difficult to control for extraneous and confounding variables (such as age, health, mood, and life experiences of research participants) which may influence the outcome or results of the study. Though the experimental study designs are considered the “gold standard,” they may not be ideal or feasible for both ethical (random assignment means one group does not receive the service/intervention) and practical reasons (a high level of investment is required, including time, expertise, and often expense). So, using experimental designs may not allow experimenters to manipulate variables due to ethical issues and practical reasons when carrying out the study (Project STAR, 2006). Types of Experimental Designs 1. Pretest-Posttest Control-Group Design The Pretest-Posttest Control-Group Design is the classical experimental design that permits researchers to randomly assign participants to either the experimental group that receives a programme, or control group that does not receive a programme or intervention being evaluated. Groups are randomly assigned before the intervention begins, and at the end of the programme or intervention. The differences between the experimental group and control group can be attributed to the effects of the programme or intervention. Each group is tested before and after the experimental group receives the intervention (Rubin & Babbie, 2013). For example, random assignment of participants to the experimental and control groups may be made from girls (at high-risk of becoming pregnant) in a high school class. Advantages of Pretest-Posttest Control-Group Design Random assignment of the subjects to the groups (treatment group or control groups) ensures that the threats (such as history, maturation, mortality, selection, regression to the mean testing, and instrumentation) to internal validity are reduced. Disadvantages of Pretest-Posttest Control-Group Design However, reactive effect remains the major threat to external validity since subjects are exposed to pre-test (Marlow, 2011). Researchers using this design may encounter challenges in its implementations