My query is regarding the use of Least Square Means – and my first “posting” in JMP – apologies if I don’t follow correct protocol!
Our business produces animal feeds. Incoming ingredients are sampled, tested and the analytical results pulled into JMP whereby analytical trends are monitored using Graph Builder (I prefer this to Control Chart). The aim is to ascribe single nutrient values for our ingredients (say protein in soyabean meal) which is then inputted into our Formulation system to optimise animal feeds to the correct nutrient specification.
As well as this graphical output, I’m also using Analyse/Fit Model to look at statistical differences in our data (e.g. are two suppliers of our soya providing the same protein content?). I generally use the “LSMeans Tukey HSD”. The output produces the table including a simple arithmetic mean and a Least Square Mean (LSM). I confess to not knowing what the LSM really is, except to guess it’s been “modelled”!
Normally I would use the arithmetic mean (having first removed extreme outliers), but when I look at the LSM it looks (I may be wrong!) more robust and with naturally variable ingredients might, I’m thinking, give me a better numeric value for using in our formulation system. I’ve seen that in some instances the mean and LSM are identical, and in other cases these numbers are quite different.
So, if this can de distilled into one question … then, “is it valid to use LSM’s in the above application?” Thank you. John S.
