The planning behind educational research is a complex process, so in addition to establishing a research problem and purpose and reviewing the literature, researchers must determine the best experimental design that suits their needs. Although experiments may share characteristics, “their use and application vary depending on the type of design used” (Creswell, 2008, p. 310). Therefore, understanding the types of experimental designs commonly used for investigating educational issues is useful in identifying the design whose approach will contribute to the success of the research. The two main domains of experimental design include intergroup and intergroup design, which are further divided into three subcategories of experimental design based on their characteristics. On the one hand, the between-group design offers an approach in which the researcher is able to compare two or more groups of subjects exposed to varying degrees of interventions (Creswell, 2008). The between-group design is widely used in various fields given its ability to provide information comparing interventions to a control group just like most scientific experiments conducted in a scientific laboratory. In contrast, the intra-group design offers an approach oriented towards observing participants as they themselves become the control of the experiment (Creswell, 2008). Given the distinction between between-group and within-group designs, it is critical to compare and contrast the six types of experimental design that fall into each of these categories. Differences in design characteristics further subcategorize the design between groups into three experimental designs that include real experts...... middle of paper......n experimental design with appropriate adjustments to reduce threats caused by participants, from treatments and procedures (Creswell, 2008). With a significant decrease in threats, a researcher can then strongly support the relationship between variables without much ambiguity. Internal validity is important in any experiment, and given that various factors threaten it in all forms of experimental design, addressing the threats should be a priority when designing research. If we want to make a difference in education, as researchers we need internally valid research to support future research and guide educational reform in an effort to improve our children's education. Bibliography Creswell, J. W. (2008). Educational research: planning, conducting and evaluating quantitative and qualitative research. Pearson 3rd ed.