Notes on the ANOVA formulas

1. In computing the SSE, if we summed only the squares for a fixed g and divided by ng, we would have the variance, i.e., the square of the SD, of the sample from group g. So we can begin to see where the term "analysis of variance" comes from. Also, it follows from what we have just said that, if we have already computed the variances, or the SDs, of the samples, then we could use them to compute the SSE: If Varg and SDg denote the variance and standard deviation of the sample from group g, then the SSE is the sum of the products ng(Varg) = ng(SDg2)

2. Provided that we interpret ng(AVg-AV)2 as the sum of ng copies of (AVg-AV)2, there are the same total number of terms in finding SSE and SSG, namely the total number of data points N.