Design of Experiments

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A designed experiment can help you choose between alternatives and select key factors affecting a response even despite uncontrollable noise factors. You can also use Response Surface modeling to hit a certain target, reduce variability in a process, maximize or minimize a response, make a process more robust despite uncontrollable noise and even pursue multiple goals.

Basic steps of DOE

  • Define objective(s)
  • Gather knowledge about the process
  • Develop a list and select your variables
  • Assign levels to variables
  • Conduct experiments
  • Data analysis and conclusions


Items to avoid when conducting the experiment:

  1. Unwarranted assumptions of the process.
  2. Undesirable combinations of the factors.
  3. Violation of known laws of physics.
  4. Too large or small design sizes.
  5. Inappropriate confounding.
  6. Imprecise measurement.
  7. Unacceptable prediction error (Type 1 & type 2 errors).
  8. Undesirable run order.

reference amazon Systematic Approach to Planning for a Designed Industrial Experiment – technometrics.


Planning and Organizing Designed Experiments

  • Define interactions
  • Understand how to analyze interactions

Balanced experiment: each factor appears the same number of times.

Full factorial experiment: At least one trial for all possible combinations of factors and levels

One Factor at a Time (OFAT)

Explain the one factor at a time (OFAT) approach

OFAT- One Factor at a Time

OFAT- One Factor at a Time

Randomized block plans

Latin square designs

See other design types

Experimental Notation

Experiments can be abbreviated numerically.

Design Ex.

2^5 means that there are 5 factors at 2 levels.

Fractional Design Ex.

2^5-2 means that there are 5 factors at 2 levels and 2 generators. The generator determines what effects are confounded or combined with one another.

We would call this example an 1/L^g fractional factorial.

Thus, 2^5-2 is a 2 level, 5-factor, 1/4th fractional design.

Design of Experiments Examples

Add examples.

Design of Experiments Videos


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