How to Select an Appropriate DOE Tool

There isn’t a simple guideline. Which one of  the design methods you use will depend on what it is that you want to do and the kinds of variables you have.

For example:

1. Are the variables of interest continuous (or can they be treated as continuous), are they nominal, or are they a mixture of the two?

2. Are you trying to assess mixtures?

3. Are there known combinations of independent variables that either cannot be physically run or if running them would result in something you know will be other than you will need for the final results of an experiment?

4. What can you afford in terms of time/money/effort?

5. Are there restrictions with respect to randomizing the run order of your design which will require you to block your design on certain variables?

6. Is this going to be an initial investigation with a number of variables whose impact is: well defined, not well understood, of some interest because we suspect it might be important, included out of curiosity, or maybe a mix of all of the preceding.

7. Is this a situation where you are fairly certain of the effect of the variables of interest and are interested in seeing if there is anything better within the current parameter space?

8. Do you expect the relationship between the variable level and the output to be something other than a simple linear one?  If so do you have the time/money/effort/desire to check for all possible curvilinear behavior or only just a select few?

9. Do you think there might be some synergistic effects (interactions) between certain variables?  If so which ones?

etc.

Once you have the answers to questions like these then you can press on with a discussion concerning the merits of the various choices for DOE.  So, if you have something in mind please provide the answers to the above questions and either I or someone else will be happy to provide additional information/advice.

I agree with Robert’s reply and general questions. As a general model,  I like the approach of going to a stadium for a ball game.

1. What stadium am I in? Wrigley Field or Candlestick. A screening DOE as a guide for factors and levels.

2. What Section are the seats located? The screening gives some insight but know you are judging where are we and where do we need to go? So, DOE #2 is a refining step.

3. What is my row and seat number? How exact must we be? Understanding main factors, or interested in possible interactions, or is a prediction model required.

4. We ok as is or do we want Club seating with AC and food delivery service? This would a very refined design with just a few critical factors.

Most DOE teams are very excited to see the results from step 2. This either confirms assumptions or dispels them or gives an insight not previously considered. Most techies want to go to step 3 for no other reason than curiosity.

Screen, sharpen, hone, sticking it!

A great tool that often yields surprises.

Ted