Quasi-Experimental and Ex Post Facto Research Designs Compared
This paper analyzes two distinct educational research designs — a quasi-experimental study and an ex post facto study — by examining their sampling techniques, levels of measurement, statistical methods, and the inferences drawn from their results. The quasi-experimental study investigates the effect of reading strategy instruction on middle school students' science literacy, while the ex post facto study explores professional development and its relationship to school climate and educational outcomes in high-poverty middle grades schools. The paper also evaluates the reliability, validity, and generalizability of each design, highlighting the trade-offs inherent in non-randomized educational research.
- Overview of the Experimental and Quasi-Experimental Method: Defines experimental method and quasi-experimentation basics
- Quasi-Experimental Study: Science Literacy and Reading Instruction: Analysis of reading-infusion science literacy study
- Ex Post Facto Research Design: Defining features of retrospective ex post facto design
- Ex Post Facto Study: Professional Development in High-Poverty Schools: Professional development effects on middle grades outcomes
- Comparing the Two Research Designs: Key distinctions between quasi-experimental and ex post facto
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What makes this paper effective
- Applies a consistent analytical framework — variables, statistics, inferences, reliability, validity, and generalizability — to both studies, making comparison straightforward.
- Clearly distinguishes the defining features of quasi-experimental and ex post facto designs, grounding abstract methodological concepts in concrete examples.
- Honestly acknowledges the limitations of each study (e.g., single-school sampling, absence of a control group) rather than overstating findings.
Key academic technique demonstrated
The paper demonstrates comparative methodological analysis: rather than summarizing each study in isolation, it evaluates both against the same set of research-quality criteria. This technique is especially useful in education and social science courses where students must critically assess whether a study's design supports its conclusions.
Structure breakdown
The paper opens with a brief definition of experimental and quasi-experimental methods, then applies a structured breakdown to each study in turn — covering levels of measurement, statistical tools, inferences, and validity concerns. A final section contrasts the two designs directly. This parallel structure keeps the analysis organized and easy to follow.
Overview of the Experimental and Quasi-Experimental Method
The intent of the experimental method — otherwise known as quantitative research or a laboratory study — is to formulate a hypothesis, collect data, and test that hypothesis according to scientific principles that obstruct bias as carefully as possible, and then to analyze the data using statistical measures. The experimental method uses random sampling as a core component of its design.
Practical considerations usually limit the degree of control researchers have when structuring experiments. For instance, it is not always possible to randomize; researchers often must work with the sample of participants already available. This is when quasi-experimentation is employed. This particular study reviewed below is a quasi-experiment.
Quasi-Experimental Study: Science Literacy and Reading Instruction
There were two levels or conditions in this study: (1) an inquiry-based science curriculum, and (2) an inquiry-based science curriculum combined with reading strategy instruction.
Three types of relevant psychological instruments were used to measure science literacy. An ANCOVA (analysis of covariance) was then conducted, using the pretest score as the covariate and the posttest score as the dependent variable.
Even a small amount of reading on science-related topics could positively affect the science literacy of middle school students, and possibly of individuals more generally.
Reliability refers to the consistency or stability of the experimental effect — it must prove capable of replication in future studies, which is closely related to generalizability. Validity refers to the soundness of the study: whether the experiment actually explains what it claims to explain.
The generalizability and reliability of this study are somewhat problematic. Although data were drawn from 10 classes, all classes came from a single school. Characteristics particular to that school — its student body, geographical location, and local context — may prevent the results from being applied to other schools or localities.
Regarding validity, exhaustive methods were taken to prevent bias and to remain as objective as possible. Nonetheless, at least one confounding variable intruded: reading educators and two sixth-grade science teachers were included in the study, which may have introduced uncontrolled influences on outcomes.
References
Fang, Y., & Wei, Z. (2010). Improving middle school students' science literacy through reading infusion. The Journal of Educational Research, 103, 262–273.
Hough, D. L., & Schmitt, V. L. (2011). An ex post facto examination of relationships among the developmental designs professional development model… Middle Grades Research Journal, 6(3), 163–175.
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