Quasi-Experimental and Correlational Research Designs
This paper examines two broad categories of research design used when true experimental methods are not feasible. The first section analyzes a quasi-experimental nonequivalent control group pre-test/post-test design applied to studying a new reading program for first-grade students, identifying teacher style and classroom atmosphere as key threats to internal validity. The second section discusses correlational research designs, illustrating their necessity when studying subject variables such as political affiliation, minimal group membership, and socioeconomic status. The paper concludes by noting that extraneous variables in both design types — including prior history, personality, and measurement timing — prevent researchers from drawing causal conclusions.
- Introduction and Study Design Overview: Context for selecting a quasi-experimental design
- Quasi-Experimental Design: Reading Program Study: Nonequivalent control group pretest-posttest reading study
- Threats to Internal Validity: Teacher effects and classroom atmosphere as confounds
- When True Experiments Are Not Feasible: Subject variables requiring correlational methods
- Examples of Correlational Research: Political affiliation, minimal groups, and natural disasters
- Limits of Causal Attribution in Correlational Designs: Extraneous variables prevent causal conclusions
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What makes this paper effective
- Uses concrete, relatable examples — a first-grade reading program, political affiliation surveys, and natural disaster response — to ground abstract methodological concepts in real research scenarios.
- Clearly distinguishes between quasi-experimental and correlational designs, explaining why each is chosen rather than simply defining them.
- Acknowledges practical constraints (e.g., school system limitations on random assignment) that shape real-world research design decisions, demonstrating applied methodological thinking.
Key academic technique demonstrated
The paper demonstrates the technique of design justification — explaining not just what research design was selected, but why alternatives were ruled out and what trade-offs result. This is particularly evident in the discussion of why random assignment within classrooms is impractical, and how that constraint shapes which threats to internal validity remain unresolved.
Structure breakdown
The paper is organized into two clearly delineated sections. Part 1 presents a specific quasi-experimental scenario (reading program study), describes the design rationale, and analyzes its primary validity threat. Part 2 broadens the discussion to correlational research, offering three progressively general examples — political affiliation, minimal group membership, and socioeconomic/demographic variables — before concluding with a synthesis of shared limitations across both design types.
Introduction and Study Design Overview
This paper examines the effect of a new reading program on students' ability to learn to read. Because the program is designed specifically to help new readers develop basic reading skills, the researcher selects only beginning first-grade students as the population of interest. Since the subject variable — being a first-grade student — cannot be targeted by random assignment, a nonequivalent control group pre-test/post-test quasi-experimental design is selected as the preferred design (Cozby & Bates, 2012).
Quasi-Experimental Design: Reading Program Study
It is often not feasible for programs like this to randomly assign different students within the same classroom to different reading programs, as there is typically only one teacher instructing the first-grade class. Such a design would be cumbersome and would most likely be rejected by the school system. Therefore, incoming first-grade students are given a basic reading pretest at the beginning of the school year. One section — or one of the first-grade teachers in the school — then uses traditional reading instruction (control group), while a different teacher in a different classroom uses the new reading program (treatment group). At the end of the semester, both classes are evaluated on their reading abilities and progress in order to determine the effectiveness of the new reading program.
Threats to Internal Validity
The major threat to the internal validity of this study is that different teachers are using different programs. As a result, some differences in outcomes may be attributable to the teacher's style of instruction, the particular classroom atmosphere, or other teacher-related factors rather than to the reading program itself (Thompson, Diamond, McWilliam, Snyder, & Snyder, 2005). One way to control for this threat through a true experiment would be to randomly assign students in each classroom to either the treatment or control condition and have a single teacher instruct both groups differently. However, as discussed above, this approach would be highly cumbersome in practice.
References
Cozby, P. & Bates, S. (2012). Methods in behavioral research (11th ed.). New York: McGraw-Hill.
Thompson, B., Diamond, K. E., McWilliam, R., Snyder, P., & Snyder, S. W. (2005). Evaluating the quality of evidence from correlational research for evidence-based practice. Exceptional Children, 71(2), 181–194.
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