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Level II

## Definitive Screening design runs

Hi

From the DSD paper it is said that the number of runs that I have to do is 2M + 1 (Even Factor) and 2M+3 (Odd Factor), but when i use the DSD window in JMP 14 any reason that my 4 factors actually shows that I have to run 17 runs instead of only 9?

Rgrds

Irfan

2 REPLIES 2
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Staff

## Re: Definitive Screening design runs

There are a couple of aspects that determine the number of runs in the DSD now. First, later research in these designs showed that the power of the tests associated with these screening designs significantly increased when at least 4 extra runs are included, so that change is automatically in effect. You may change the number of extra runs at any time, though, including none. Second, a screening design is an advanced design for a specific purpose that might work only if the key assumptions hold. The sparsity of effects principle is one of the key assumptions.

So if you have less than five factors, JMP designs the DSD for 5 factors. (Essentially that behavior is saying that only 4 factors is not really a screening case so I need to protect you if you want to use a DSD.) That means the minimum number of runs is 2*5+3 = 13. Then the 4 extra runs gets you to 17 runs.

See Help > Books > Design of Experiments. There is an entire chapter devoted to the latest implementation of DSD in your version of JMP.

Learn it once, use it forever!
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Level II

## Re: Definitive Screening design runs

Hi Mark,

Thanks

Rgrds

Irfan

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