topic Re: Interpretation of leverage plot axes in Discussions

Interpretation of leverage plot axes

atwee — Fri, 09 Jun 2023 00:21:40 GMT

Hello,

I am trying to understand how to interpret the leverage plot axes-- specifically why negative x and y values are plotted when my data have none of these. I understand, I supposed, that negative y values could be the result of model uncertainty, but why the x values?

For sake of discussion, if it matters, I am running a multiple regression of rainfall amount (cm), development level of watershed (% developed) and looking at the creek response (flow). I have no negative values, yet the leverage plot shows X values well below my actual data range.

Thanks

Re: Interpretation of leverage plot axes

Byron_JMP — Tue, 22 Sep 2020 18:59:19 GMT

JMP adds the mean of Y to the Y-residuals and the mean of X to the X-residuals. So I expect you may have some very negative residuals ?

detail

https://www.jmp.com/support/help/en/15.2/index.shtml#page/jmp/leverage-plots.shtml

Re: Interpretation of leverage plot axes

atwee — Tue, 22 Sep 2020 19:06:15 GMT

Thank you. Yes there are some fairly negative residuals but the model appears very good and the Y residuals are nicely scattered.

Re: Interpretation of leverage plot axes

Byron_JMP — Tue, 22 Sep 2020 19:11:06 GMT

As long as the magnitude of the residuals aren't concerning... (and without looking at anything) you're probably OK.

When I have extreme values (high or low X) that are far from the center of the data (Y) I'll take a little closer look at that point because it exerts a higher degree of "leverage" on the regression.