For 2 variables, CCD and for 4 Variables, BBD can be chosen, how can we choose the designs based on the number of variables and based on the model type?
Ok, first CCD = Central Composite Designs and BBD = Box-Benkhen Designs, right?
So, I believe you are working with response surface models. Do you want to choose design for quadratic models?
Alan you r right, on what basis the model was choosen either based on the No. of variables or else base on the model type we choose & fix the variables which one is exactly wright way to proceed. Among CCD & BBD which is effective for 2 and 3 variables. I want to chooses the exact design for Q models. I need ur valuable suggestions.
You can use this two types of designs. They are very powerful and useful. But not flexible if you want to define your model under study and if you have a limited number of runs to perform.
So I believe that you should construct the design for your particular situation using optimal design of experiments. You can find these functions in the JMP Software (free trial). You will need your model under study, the number of runs, among other things.
Now, to use the methodology in a correct way, you need to state what is your study for. These are some possibilities:
- Construct a design that allows you to have good estimates of your parameters. Using D-optimal designs
- Construct a design that allows you to have good prediction power. Using I-optimal designs
- Construct a design to make some screening to your factors (quadratic, interactions, main). Definitive Screening Designs See http://blogs.sas.com/content/jmp/2012/01/30/introducing-definitive-screening-designs/
http://www.jmp.com/support/help/Creating_Response_Surface_Experiments.shtml
Thank you for your response and useful information regarding my query. thanks for sharing your valuable time.
How many factors do you want to test? 2 or 4? Are your factors discrete or continuous? How many levels can you have for each factor?
In general, I would go with an Optimal design. They allow you to fit the experiment/model to your design space. BBD and CCD require you to fit your design space to your experiment. Optimal designs also let you use categorical variables.
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