standard deviations in one way analysis of variance with blocksHello,
I used the fit y by x platform of JMP to analyze the effect of two products on a response. I also have a blocking variable. The block means report is the following:
Means and Std Deviations
Level Number Mean Std Dev Std Err Mean Lower 95% Upper 95%
A 52 3.75 0.563468 0.078139 3.631591 3.945332
B 52 3.97 0.563468 0.078139 3.7854372 4.0991782
Why are standard deviations the same (the actual standard deviations estimated from each sample are different)? What is the formula behind
Many thanks.
Consumer and Market ResearchRe: standard deviations in one way analysis of variance with blocksA primary assumption of the ANOVA model is that the errors are constant across all groups. So the 'sum of squared errors' are 'pooled' across all groups. The estimates are not the simple standard deviation of each group as you would get from Distribution with By( group ) role.
The same assumption is made by the two-sample t-test, unless a correction is made.
