Design of experiments (DOE)

1. Design of experiments (DOE) Steps Define problem Define experimental objectives Select factors that influence quality Select control & noise factors Select levels for factors Select orthogonal arrays Select interactions Conduct tests Analyze results

2. Level Factor 1 2 flour 21/3cups all-purpose 21/3cups special sugar 2 Tsp 21/2 Tsp salt 1 tsp 1/2 tsp butter 1 Tsp 1 Tsp margarine milk 1 cup homogenized 1 cup low-fat dry yeast 1 tsp brand A 1 tsp brand B Design of experiments (DOE) Breadmaking problem:

3. Design of experiments (DOE) How many loaves of bread to get "best" set of ingredients? 6 factors, each w/ 2 levels ––> 26 = 64! Taguchi method (Genechi Taguchi) says only a few needed

4. Factors and factor levels Trial A B C D 1 1 1 1 2 1 1 1 1 2 1 1 1 1 2 1 1 1 1 2 Design of experiments (DOE) Testing methods

5. Factors and factor levels Trial A B C 1 1 1 1 2 2 2 1 2 2 2 1 Design of experiments (DOE) Testing methods Better…….."orthogonal" Standard L4 orthogonal array

6. Design of experiments (DOE) Which OA to use? Depends on: # of factors & interactions # of levels for each factor Use L4, L8(7 factors), L12(11 factors), L16(15 factors),…..OAs - determined by # trials to be run # of levels usually 2 or 3

7. Factors and factor levels Trial A B C(=AxB) 1 1 1 1 2 2 2 1 2 2 2 1 Design of experiments (DOE) Some factors may interact. Then: