is about
data item
residual
residual mean square
Thomas Nichols
http://en.wikipedia.org/wiki/Mean_squared_error#Regression
MSE
a residual mean square is a data item which is obtained by dividing the sum of squared residuals (SSR) by the number of degrees of freedom
error mean square
used as an unbiased estimator of teh variance for a regression model
Philippe Rocca-Serra
Alejandra Gonzalez-Beltran
https://github.com/ISA-tools/stato/issues/35
Camille Maumet
http://support.minitab.com/en-us/minitab/17/topic-library/modeling-statistics/anova/anova-statistics/understanding-mean-squares/
ready for release