Design of experiments means the planning process that needs to go into any experiment, survey or study in order for the results to be valid. The terms “Experimental Design” and “Design of Experiments” are used interchangeably and mean the same thing. However, the medical and social sciences tend to use the term “Experimental Design” while engineering, industrial and computer sciences favor the term “Design of experiments.”
Design of experiments involves:
- The systematic collection of data
- A focus on the design itself, rather than the results
- Planning changes to independent (input) variables and the effect on dependent variables or response variables
- Ensuring results are valid, easily interpreted, and definitive.
The most important principles1 are:
- Randomization: the assignment of study components by a completely random method, like simple random sampling. Randomization eliminates bias from the results.
- Replication: the experiment must be replicable by other researchers. This is usually achieved with the use of statistics like the standard error of the sample mean or confidence intervals.
- Blocking: controlling sources of variation in the experimental results.
You’ll find hundreds of videos and articles on this site to help you with the statistics behind design of experiments (including confidence intervals, sampling and hypothesis testing). These articles will guide you through design of experiments basics:
- What is Clustering?
- What is the Cohort Effect?
- What is Counterbalancing?
- Data Collection Methods
- What is an Effect Size?
- What are generalizability and transferability?
- What is Grounded Theory?
- The Placebo Effect
- What is the Practice Effect?
- What is Qualitative Research?
- What is Quantitative Research?
- Random Selection and Assignment.
- Research Methods (includes Quantitative and Qualitative).
- Recall Bias.
- What is Response Bias?
- What is Survey Sampling?
Design of Experiments: Types
- Balanced and Unbalanced Designs.
- Between Subjects Design
- What are Case Studies?
- What is a Case-Control Study?
- What is a Cohort Study?
- Completely Randomized Design.
- Cross Sectional Research.
- What is Experimental Design?
- Factorial Design.
- Longitudinal Research.
- Matched Pairs Design.
- Parallel Design.
- Observational Study.
- Pretest Posttest Design.
- Prospective Study.
- What is Quasi-Experimental Design?
- Repeated Measures Design.
- Retrospective Study.
- Stepped Wedge Designs.
- What is Survey Research?
- What is Randomized Block Design?
- Within Subjects Design
Validity in Design of Experiments
- What is Concurrent Validity?
- What is Construct Validity?
- What is Consequential Validity?
- What is Convergent Validity?
- What is Criterion Validity?
- What is Ecological validity?
- What is External Validity?
- What is Face Validity?
- What is Internal Validity?
- What is Predictive Validity?
Variables in Design of Experiments
- What is a Confounding Variable?
- What is a Control Variable?
- What is a Criterion Variable?
- What are Endogenous Variables?
- What is a Dependent Variable?
- What is an Explanatory Variable?
- What is an Intervening Variable?
- What is a Manipulated Variable?
- What is an Outcome Variable?
- Accuracy and Precision.
- Block plots.
- Cluster Randomization.
- What is a Experimental Group (or Treatment Group)?
- What is a Control Group?
- What is a Randomized Clinical Trial?
- The Hawthorne Effect.
- The Hazard Ratio.
- Inter-rater Reliability.
- Main Effects.
- Order Effects.
- Systematic Errors.
Reference: Penn State: Basic Principles of DOE