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DOE Analysis Steps
The following are the basic steps in a DOE analysis.
1.
Look at the data. Examine it for outliers, typos and obvious problems. Construct as many graphs
as you can to get the big picture.
Response distributions (
histograms
,
box plots
, etc.)
Typical DOE plots (which assume standard models for effects and errors)
Main effects mean plots
i
nteraction plots
2. Create the theoretical model (the experiment should have been designed with this model in
mind!).
3. Create a model from the data. Simplify the model, if possible, using stepwise regression methods
and/or parameter p-value significance information.
4. Test the model assumptions using residual graphs.
If none of the model assumptions were violated, examine the ANOVA.
Simplify the model further, if appropriate. If reduction is appropriate, then return to
step 3 with a new model.
If model assumptions were violated, try to find a cause.
Are necessary terms missing from the model?
Will a transformation of the response help? If a transformation is used, return to step 3
with a new model.
5. Use the results to answer the questions in your experimental objectives -- finding important
factors, finding optimum settings, etc.

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