Experimental and Non-Experimental Research Designs
Structure • Control • Validity • Comparison
1. Introduction: Meaning of Research Design in Psychology
A research design refers to the overall plan or blueprint that guides the collection, measurement, and analysis of data in psychological research. It determines how variables are studied, how control is maintained, and how conclusions are drawn.
In psychology, research designs are broadly classified into:
- Experimental Designs — where variables are manipulated
- Non-Experimental Designs — where variables are observed without manipulation
Experimental designs aim to establish causation, while non-experimental designs focus on description, association, and prediction.
graph TD RD[Research Design] --> ED[Experimental Design] RD --> NED[Non-Experimental Design] ED --> CAUSE[Causation] NED --> ASSOC[Association / Description]
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2. Characteristics of Experimental Design
An experimental design is characterised by active manipulation of variables and systematic control to test cause–effect relationships.
Key Characteristics
- Manipulation of independent variable
- Control over extraneous variables
- Random assignment of participants
- Comparison between groups
To determine whether changes in the dependent variable are directly caused by the independent variable.
graph TD IV[Independent Variable] --> DV[Dependent Variable] IV --> EXP[Experimental Group] CTRL[Control Group] --> DV RAND[Random Assignment] --> EXP RAND --> CTRL
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3. Strengths and Limitations of Experimental Design
Strengths
- High internal validity
- Clear cause–effect conclusions
- Replicable procedures
- Scientific precision
Limitations
- Artificial laboratory settings
- Ethical constraints
- Limited applicability to complex social behaviour
- Lower ecological validity
Memory experiments in laboratories establish causation, but may not fully reflect real-life remembering.
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4. Characteristics of Non-Experimental Designs
Non-experimental designs study psychological phenomena as they naturally occur, without manipulation of variables. The researcher observes, measures, or analyses existing conditions.
Key Characteristics
- No manipulation of variables
- Focus on description, correlation, or prediction
- Greater naturalism
- Ethically suitable for sensitive issues
graph TD NED[Non-Experimental Design] --> DESC[Description] NED --> CORR[Correlation] NED --> PRED[Prediction]
Survey studies, observational research, case studies, correlational designs.
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5. Strengths and Limitations of Non-Experimental Designs
Strengths
- High ecological validity
- Ethically flexible
- Suitable for large-scale and real-world issues
- Useful for exploratory research
Limitations
- Cannot establish causation
- Greater risk of confounding variables
- Lower internal validity
Correlation does not imply causation — a key limitation of non-experimental designs.
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6. Comparative Overview: Experimental vs Non-Experimental Designs
| Aspect | Experimental Design | Non-Experimental Design |
|---|---|---|
| Variable Manipulation | Present | Absent |
| Control | High | Low to moderate |
| Causality | Can be established | Cannot be established |
| Ecological Validity | Lower | Higher |
| Ethical Flexibility | Limited | High |
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