topic Re: "Actual by Predicted plot" - How confidence intervals are really calculated ? in Discussions

"Actual by Predicted plot" - How confidence intervals are really calculated ?

Julianveda — Sun, 16 Jul 2023 07:26:44 GMT

Hello Community,

My Question:

I have a question concerning how I can access the confidence intervals of the Actual by predicted graph below:

I attach the jmp file if you want to try yourselves. Now I am gonna tell you what I have tried up to know:

What I have tried:

I have save the columns “mean confidence limit formula as shown below:

However, when I try to reproduce the “Actual by Predicted plot”, the confidence intervals don’t look similar :

Actal by predicted plot:

Graph done in Graph builder with the saved columns (predicted, lower and upper confidence intervals):

So the saved columns clearly do not correspond to the confidence intervals in the “actual by predicted plot”

However, I realized that the saved confidence interval columns are actually the confidence intervals that appear in the profiler. Look at the two pictures below, one from the profiler and the other one built in the Graph builder:

This is interesting, but my original question is still unanswered:

How the confidence intervals from the “actual by predicted plot” are calculated ?

I also tried calculating them by myself in excel using the statistical equations for this, but still the confidence intervals I find are different from the “actual by predicted plot”:

Confidence interval calculated with t=0.05

Very different from

Conclusion:

Neither in JMP nor by my own calculation I have not been able to find the right way in which the confidence interval in the “actual by predicted” are actually calculated.

Could please someone help me to understand ?

Thank you,

Julian

Re: "Actual by Predicted plot" - How confidence intervals are really calculated ?

jthi — Sun, 16 Jul 2023 14:02:27 GMT

Usually good starting point is using Help tool found from JMP's toolbar (?). Hover over the part you are interested in the analysis while the ? tool is enabled

and it will open help page related to that https://www.jmp.com/support/help/en/17.0/#page/jmp/effect-leverage-plots.shtml?os=win&source=application#ww184200 . Use this as the starting point, then if you don't find what you are looking for check the left side of help page and look for "Statistical Details...." https://www.jmp.com/support/help/en/17.0/#page/jmp/statistical-details-for-leverage-plots.shtml#ww1502500 . Hopefully these provide at least some additional information

Re: "Actual by Predicted plot" - How confidence intervals are really calculated ?

Julianveda — Mon, 17 Jul 2023 06:57:04 GMT

Thank you @jthi for the links. I have already seen the one about the leverage plots but not the one of the statistical details. I'll have a look into that to see if it can help me. Thank you also for the tip of (?) tool; it's may be simple but I did not know about it :)

Re: "Actual by Predicted plot" - How confidence intervals are really calculated ?

Victor_G — Mon, 17 Jul 2023 07:23:47 GMT

Hi @Julianveda,

The questions about "Actual vs. Predicted" plot are quite common in this Community, you can also look at some previous posts with the provided answers, it may already solve some of your questions :)
Example here : https://community.jmp.com/t5/Discussions/Actual-by-predicted-plot-confidence-region/m-p/641519

I hope this will also help you,