It's called LSD (least significant distance). When you are doing multiple comparison test, you get the table called Abs(Dif) - LSD To get the LSD value subtract the value from the table above from the difference between the means found in the difference matrix in the same window.
When I separate means using Tukey's HSD, I get a LSMeans Differences Tukey HSD Table. Is there not a simply way to get JMP to generate the LSD value? I ask because I still don't follow what to subtract from what, and I deal with multi-factorial ANOVAs, so I can't do it all by hand.
After you've run your "Fit Model" dialog, go to the "Effect Details" tab, and expand that. You'll find there a tab for each of the factors you've included in the model, each of which has a red triangle on the tab. Click on that red triangle, and you'll get a menu from which you can select either "LSMeans Student's t" or "LSMeans Tukey HSD". If you do that you'll get two tables: the first one shows the SED, lower confidence limit and upper confidence limits (from which you can calculate the LSD) of each pairwise comparison between every level of your factor, and the second one gives you a "letters chart" in which all the means are ranked from largest to smallest, with columns of letters joining all groups of levels that are not significantly different at whatever significance level you wanted. The letters chart gives you an immediate feel for what's significantly different from what, and I find is also a very convenient summary table for including in reports, not least because you can right-click on it to create a data table which you can then export directly as an Excel spreadsheet.
The cutoff level is normally alpha=0.05, but you can change that - see this thread for details: http://support.sas.com/forums/thread.jspa?messageID=29987産
I follow expanding the tabs, but I am still confused:
1. From the LSMeans Student's T tab, how is SED calculated from the LSmeans below the matrix shown?
2. Once the SED is calculated, how do you calculate LSD?
I often use the letters chart, but if I have many response variables I get an alphabet soup of information that can be unwieldy in a paper, which is why I sometimes just prefer to include an LSD value.
I guess I am still surprised that JMP doesn't just have a function to give you an immediate value for SED and LSD when you have many response variables.