Design of Experiments (DOE) is a systematic statistical methodology for planning, conducting, and analyzing controlled experiments to understand and optimize complex processes and systems. Originally developed by Ronald A. Fisher in the 1920s for agricultural research, DOE has evolved into an indispensable tool across manufacturing, pharmaceuticals, materials science, biotechnology, and virtually every field requiring empirical optimization. DOE enables experimenters to efficiently extract maximum information from minimum experimental runs by strategically manipulating multiple factors simultaneously, rather than the wasteful one-factor-at-a-time approach. The fundamental insight underlying DOE is the principle of effect sparsity—relatively few factors and interactions dominate system behavior, allowing fractional designs to capture essential relationships while dramatically reducing experimental cost and time.
What This Cheat Sheet Covers
This topic spans 24 focused tables and 166 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.
Table 1: Fundamental Concepts & Terminology
Before running any experiment, fluency with DOE vocabulary is essential — misusing terms like replication versus repetition or confusing a factor with a covariate leads to incorrect designs and flawed analyses. These definitions form the shared language across all DOE methods.
| Concept | Example | Description |
|---|---|---|
Temperature, Pressure, Catalyst | • Controllable input variable studied for its effect on the response • can be continuous, discrete, or categorical. | |
Low (−1), High (+1) | Specific setting or value at which a factor is held during an experimental run. | |
Yield (%), Strength (MPa) | Measured outcome variable (dependent variable) that depends on factor settings. | |
T=200°C, P=5 bar, Catalyst A | Specific combination of factor levels applied to an experimental unit. | |
Batch, Specimen, Patient | • Smallest entity to which a treatment is independently applied • defines the replication level. | |
Single test execution | One execution of a specific treatment combination in the experiment. | |
3 batches per condition | • Independent repetition of treatment combinations • provides estimate of pure experimental error. | |
Random run order assignment | • Random assignment of treatments to units and run order • controls for unknown nuisance variables. |