Quasi-experimental design can be a valid option for determining the causal effects of interventions on outcomes when random assignment is not possible, not practical, or unethical. Quasi-experimental designs allow researchers to make causal inferences while attempting to approximate the conditions of a true experiment and operating within the limitations of real-world contexts.
Quasi-experimental designs are useful approaches for intervention research without random assignment, and they can be effectively one approach for applied research designs in education, healthcare, and social sciences. [1]
Quasi-experimental design is a quantitative research design that examines the impact of an intervention on a group, generally known as a target population, without random assignment of groups (treatment and control). Quasi-experimental design is action-focused and shares many similar characteristics of experimental design – pretest, post-tests, control groups, etc. – but lacks random assignment (Schmidt & Brown, 2015), which is the fundamental difference. [1]
| Criteria | Experimental Design | Quasi-Experimental Design |
|---|---|---|
| Random Assignment | Yes | No |
| Internal Validity | High | Moderate to Low (depends on controls) |
| Control over Variables | Strong | Limited |
| Ethical Suitability | Less suitable for real-world interventions | More suitable for field or educational interventions |
| Example | RCT of new drug | Evaluating curriculum reform in public schools |
| Type | Description | Example in Research | Advantages | Limitations |
|---|---|---|---|---|
| Non-Equivalent Control Group Design | Compares a treatment group with a non-randomized control group | Telerehabilitation Intervention in Transitional Care for People with COVID-19: Pre-Post Study with a Non-Equivalent Control Group [2] | Allows group comparison | Groups may differ in ways unrelated to intervention |
| Interrupted Time Series Design | Observes data over time before and after intervention | Improving Causal Inference in Observational Studies: Interrupted Time Series Design [3] | Good for longitudinal analysis | May be affected by other time-related factors |
| Regression Discontinuity Design | Assigns participants to treatment/control based on a cutoff score | Science of Science: A survey [4] | Strong causal inference | Requires large sample and precise cutoff |
| Single-Group Pretest–Post-test Design | Measures outcomes before and after treatment in the same group | Moving Beyond Simplistic Research Design in Health Professions Education: What a One-Group Pretest–Post-test Design Will Not Prove [5] | Easy to implement | No control group for comparison |
| Post-test-Only Design with Non-equivalent Groups | Only measures outcomes after intervention in two or more non-randomized groups | Can student–peers teach using simulated-based learning as well as faculty: A non-equivalent post-test-only study [6] | Simple data collection | No baseline data for comparison |
Quasi experimental research design in education is needed when random assignment of either students or institutions is not possible. For example, policy interventions at the district or national level (such as digital education programs) usually use non-equivalent group designs to measure impact.
Example Scenarios:
| Discipline | Example | Design Used |
|---|---|---|
| Cardiology | Designing and evaluating ECG interpretation software for undergraduate nursing students in Iran: a non-equivalent control group pretest-post-test design [7] | Non-Equivalent Control Group Design |
| Psychology | Mental Health Delivery Method Outcomes for the Postsecondary Student: A Quantitative Quasi-Experimental, Non-Equivalent Control Group Pretest-Post-test Study [8] | Non-Equivalent Control Group Pretest-Post-test Study |
| Paediatric | Development and evaluation of a paediatric nursing competency-building program for nursing students in South Korea: a quasi-experimental study [9] | Quasi-experimental study, non-equivalent control group pretest-post-test design |
| Nursing | Effect of the Management in Nursing course on students’ time management and career planning attitudes: A single-group pre-test post-test study [10] | A single-group pre-test post-test study |
| Cardiology | Integrating mixed reality preparation into acute coronary syndrome simulation for nursing students: a single-group pretest-posttest study [11] | A single-group pre-test post-test study |
| General | Teacher training and HIV/AIDS prevention in West Africa: regression discontinuity design evidence from the Cameroon [12] | Regression discontinuity design |
| Health Care | Use of Interrupted Time Series Analysis in Evaluating Health Care Quality Improvements [13] | Interrupted Time Series Design |
| Health Service | Emergency department-based medication review on outpatient health services utilization: interrupted time series [14] | Interrupted Time Series Design |
| Medical Intensive Care | Mortality, Morbidity, and Costs After Implementation of a Vasopressin Guideline in Medical Intensive Care Patients With Septic Shock: An Interrupted Time Series Analysis [15] | Interrupted Time Series Design |
| Advantages of Quasi-Experimental Designs | Disadvantages of Quasi-Experimental Designs |
|---|---|
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Quasi-experimental designs effectively address research settings without control or randomization; in fact, they have aspects of both observational research with an intervention and controlled experiments. Quasi-experimental designs are commonplace in the fields of education, public health, and policy analysis which mix elements of both observational research and experimentation. If researchers understand the types, uses, and limitations of quasi-experimental designs, it can help them to develop studies that achieve an appropriate level of feasibility without sacrificing scientific rigor.
Quasi-Experimental Design: Definition, Types, and Examples? Pubrica offers end-to-end research design, analysis, and reporting support.