I want to perform a DoE in order to optimize an extraction method. My plan is to start with a screening of the main factors using Plackett Burman followed by a central composite design in order to do a response surface. Before making a Design tube I should choose a Run order (sort left to right, sort right to left, randomize...) and I do not know which run order I should choose for each of my designs and why?
thank you in advance
I am fond of Plackett-Burnham designs but I think in this case you might want to use an alternate. Sequential experimentation using classical designs usually favors the Central Composite Design (Box-Wilson) because you can run the two-level screening portion with a few center points and determine if the rest of the runs are helpful.
I think that you should consider a definitive screening design in this case.
And you should randomize the run order AND reset all the factor levels before each run. If you can't (or won't) then use a Custom Design and define which factors are hard to change.
Welcome to the JMP Community.
While I agree with Mark , that you should consider sequential experimentation, I would not choose Plackett Burman or DSD. I would choose a fractional factorial so you can easily know the aliasing (and there is no partial aliasing).
1. How many factors are you considering for screening?
2. Ensure you choose bold level setting to increase the likelihood the factors will demonstrate their effects.
3. Make a list of predicted effects (main effects and 2-factor interactions). Prioritize this list. If you have 2-factor interactions high on the list, consider higher resolution designs, if they are at the bottom, Res. II is adequate.
4. The most challenging part of experimentation is not the matrix for factors, but the strategy that you use for handling noise. If you cannot identify the noise is in the extraction process, then you would randomize to prevent the noise from being confounded with factor effects (and potentially to get an unbiased estimate of the noise). If you are able to identify the noise variables are in the extraction process (using tools such as a process map), then your options are better (RCBD, BIB, Repeats, split-plots, covariates, etc.) To quote G.E.P. Box:
"Block what you can, randomize what you cannot"
Thank you for your answer. This is my first experience with DoE therefore I will need further details.
As I said I want to optimize an extraction method and according to some published articles they start with a screening design using the Plackett Burman (it gives good results even it is studying just the mean effects) and after the screening they use a central composite design. In my field this is the most used strategy, a screening followed by a response surface design. And here are further details about what I want to do
- The extraction technique is pressurized liquid extraction
- I have 8 for screening and from them I am planning to choose 3 for a response surface design.
- I have 2 responses to maximize
- They are no restrictions on randomization, I can randomize my trial order if it is necessary
I'll let others give you specific advice on your experiment, but I'll encourage you to take a look at two good tutorials on DOE. They won't take you very long and they'll give you some good background on the theory and practice of Design of Experiments.
The first is the Design of Experiments module of Statistical Thinking for Industrial Problem Solving. Here's an overview of the module:
The second is the JMP DOE Introductory Kit. This will give you a good overview of the process of designing, conducting, and analyzing your experiment in JMP itself.
These are both really good resources to help get you started.