Why does the Sum of Squares under "Effect Tests" not add up to the overall model's Sum of Squares?

[#1]

Hi all,

I fitted a simple model with one continuous and one nominal variable using Standard Least Squares. Now I am wondering why the sums of squares seem to mismatch under Analysis of Variance and Effect Tests. I am on JMP 18.0.1.

3.16 and 0.01 do not give the overall model's SS of 3.37. It's like some 0.2 are missing. Could anyone please explain why that is?

This particularly puzzles me because I am looking at analysis of the same data in minitab provided by colleagues, and there the factor "Month" indeed gets the increased SS of 0.209. All the other stuff like DF and SS of everything else matches. In the end, this has implications for the p-value to judge the significance of "month" for the fit, which is why this bothered me in the first place.

Regards,

Konstantin

[#2]

Yeah, "stability" is to monitor any decline or change of any attribute of the drug over time. Thanks for the tip about using the sequential tests in JMP. In this context, you usually have the three (maybe historically for practical reasons) batches and are interested whether they behave the same. So, you start off with batch, time, and their cross-term. You first test if you can throw out the cross-term, meaning all slopes are equal. Then, you would like to throw out "batch", i.e., show that the intercepts are equal. You throw the datapoints all in one plot and fit a line. Sometimes you can have more factors, which you would ideally like to have no influence. Thus, month/time is usually the last man standing here.

I've seen a great course here on the JMP site about mixed models and how they can be applied to this topic, but it comes with a disclaimer that such an approach is simply not compliant with the mentioned guideline, so there we go

[#3]

Hi @Bashburz1 : not sure if you are aware, by there is a module for stability analysis in JMP.

https://www.jmp.com/support/help/en/18.1/index.shtml#page/jmp/stability-analysis-in-the-degradation-...

It does the same thing as in the fit model platform, but it has a few options that are specific to stability analysis per ICH Q1E. 

[#4]

I wasn't aware, thank you! It's still neat to understand the steps and do it manually, but that module literally does this job for oneself.

[#5]

That's right, month is simply the unit of time.