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DOE for a single component with different sources & levels

I am trying to optimize the maltodextrin component of a formulation. There are 3 different maltodextrins I would like to assess (different suppliers - categorical), and I would like to run each at 3 concentrations/levels.

 

It doesn't make sense to put the 3 different maltodextrin options as different factors, because they will never be used together - the idea is to choose the best one. I could do 3 separate one-factor DOEs, but this seems inefficient. 

 

Is there a good design to simultaneously assess which maltodextrin is the best and which concentration is the best?

 

Thanks!

DOERe: DOE for a single component with different sources & levels

@thaumi .  Welcome to the JMP community.  There are multiple options to achieve what you may want.  Just to make sure, you are not interested in understanding causal structure, you are just trying to "pick the winner", correct.  I can offer some of my thoughts/questions, but I admit I'm a devout determinist, so I apologize in advance:

1. If you are trying to determine which supplier is the best, I'm not sure DOE would be my recommended data collection strategy.  Why, because I'm not sure how you would represent the supplier as a "level" with the likely within supplier variation.  I might suggest a nested sampling plan where you take multiple samples of multiple concentrations and maybe even nest a layer for measurement precision.

2. How confident are you in the measurement system? 

3. Are the concentrations the same for all suppliers?

4. How many samples of "materials" would you need to have a degree of confidence that those samples represent the variability in the processes?

 

Re: DOE for a single component with different sources & levels

@statman raises some good points for you to consider. I was probably being too naive (or assuming too much), but your problem description led me to think you had two factors. One is Supplier, which is a 3-level categorical variable. The other factor is Concentration which should probably be continuous (you only specify the number of levels based on the model you want to fit -- quadratic effects require 3 levels). Given this, I thought the model would be: Supplier, Concentration, Supplier*Concentration, Concentration*Concentration and MAYBE Supplier*Concentration*Concentration.

 

There are LOTS of assumptions in my thinking, so please be very thoughtful about what you are trying to do and why. Thinking about and answering @statman's questions will certainly help you out.

Re: DOE for a single component with different sources & levels

To add a couple additional questions/thoughts to supplement @Dan_Obermiller and @statman 's thoughts...and harkening back to my days as a supplier quality manager...there are many non-statistical criteria that go into supplier selection especially when you say you are looking for the 'best'...whatever that means...

 

1. Cost (price).

2. Long term variation from a quality/composition point of view.

3. Lead time. This is important if one of your organization's goals are minimizing work in process inventory, single piece flow process design, and just general good Lean practices.

4. Minimum order quantity restrictions?

5. On time delivery performance.

6. Confidence/risk in assured supply. For example...in this COVID world...will the supplier have to shut down for pandemic reasons?

 

My experience unfortunately was that the criteria above almost always overwhelmed whatever engineering/scientific recommendations that were learned or observed in performance testing/evaluation. I hope your organization is different?