Our World Statistics Day conversations have been a great reminder of how much statistics can inform our lives. Do you have an example of how statistics has made a difference in your life? Share your story with the Community!
Choose Language Hide Translation Bar
Highlighted
Ella
Level I

Re: 3rd power parameter DOE

 
Highlighted
Ella
Level I

Re: 3rd power parameter DOE

First I made custom Design with d optimality for 2nd order model and augmented Design with I Optimality for 3rd order model. Is it right ?
Highlighted
statman
Level VII

Re: 3rd power parameter DOE

AFAIK, in the custom design platform, as long as you select Necessary (vs. If Possible), JMP will create a design that will allow for estimation of those effects.

Highlighted
statman
Level VII

Re: 3rd power parameter DOE

I do have wonder what it is you are working on where you suspect cubic effects? Even if they exist, they will be difficult to "manage". Seems you might want to investigate alternative repossess variables that may be robust to those type of effects?
Highlighted

Re: 3rd power parameter DOE

I do not mean to contradict one of my colleagues, but how does one specify the factors, model, and number of runs in order to get 'correct design' without correlated estimates?

 

I added four continuous factors representing concentration, temperature, time, and pressure. I added terms for the second and third power of each factor to the linear model. I used the default number of runs. This example is clearly not one of the correct results:

 

design.JPG

 

I simulated the response so that I could launch Fit Least Squares platform. The response is not involved in the correlation of the estimates, which is also indicated by VIF > 1 in the parameter estimates report. Here is the design:

 

table.JPG

 

Here is the report using the default coded levels. VIF around 10 indicates a correlation around 0.9.

 

coded.JPG

 

Here is the same analysis but without coded levels. The coding clearly helps:

 

uncoded.JPG

 

What is the use of the map of correlations if it does not represent the actual correlations? (I think that it does.)

Learn it once, use it forever!
Highlighted

Re: 3rd power parameter DOE

Just to clarify, the coding used in the Custom Designer will show the correlations, which you can't get around due to the natural correlation built in by taking -1 and +1 to the third power. From the design perspective, you're still finding the D-optimal design, but the diagnostics make it look "bad".

In the future, I can see us using an orthogonal polynomial coding approach to make to make the higher order terms not look as bad as this. Note that you'll see the same issue between x^2 and x^4 if you were to include up to the fourth power.

To summarize, it's not that there's anything wrong with the design, or the correlations, but it's something that we're certainly aware of causing confusion and hope to better address this in a future version.

Hope this helps,
Ryan
Highlighted
statman
Level VII

Re: 3rd power parameter DOE

@ryan_lekivetz, sorry I apparently did a poor job of explain what we discussed yesterday. Thanks for your clarification.
Highlighted

Re: 3rd power parameter DOE

@statman , just making sure we're all on the same page. 

 

It was great talking to you yesterday, and it was great to put a face with the name. Very much appreciate your help on the community forums.

 

Cheers,

Ryan

Highlighted
Ella
Level I

Re: 3rd power parameter DOE

I see, thank you very much for you explanations. but i still do not clear about which tipe of Design i have to use to be abla to construct a good model ( a model without correlations) with main effects + 2 nd and 3rd order interractions + 2 nd and 3rd order powers.

Is custom Design with I optimality correct? Or do you suggest me something else?
Article Labels