How to Test and Revise DOE Models¶

Tools for testing, revising, and selecting models

All the tools and procedures for testing, revising and selecting final DOE models are covered in various sections of the Handbook. The outline below gives many of the most common and useful techniques and has links to detailed explanations.

Outline of Model Testing and Revising: Tools and Procedures

An outline (with links) covers most of the useful tools and procedures for testing and revising DOE models

• Graphical Indicators for testing models (using residuals)

  • Response vs predictions
  • Residuals vs predictions
  • Residuals vs independent variables
  • Residuals lag plot
  • Residuals histogram
  • Normal probability plot of residuals

• Overall numerical indicators for testing models and model terms

  • R Squared and R Squared adjusted
  • Model Lack of Fit tests
  • ANOVA tables (see Chapter 3 or Chapter 7)
  • p-values

• Model selection tools or procedures

  • ANOVA tables (see Chapter 3 or Chapter 7)
  • p-values
  • Residual analysis
  • Model Lack of Fit tests
  • Data transformations for normality and linearity
  • Stepwise regression procedures
  • Normal or half-normal plots of effects (primarily for two-level full and fractional factorial experiments)
  • Youden plots