Statistics Tip: In ANOVA, Sum of Squares Within (SSW) is the sum of Variations within each of several datasets or Groups.

In ANOVA, Sum of Squares Total (SST) equals Sum of Squares Within (SSW) plus Sum of Squares Between. (SSB). That is, SST = SSW + SSB.  In this Tip, we'll talk about Sum of Squares Within, SSW. In ANOVA, Sum of Squares Within (SSW) is the sum of Variations within each of several datasets or Groups.

The following illustrations are not numerically precise. But, conceptually, they portray the concept of Sum of Squares Within as the width of the “meaty” part of a Distribution curve – the part without the skinny tails on either side. 

​Here, SSW = SS1 + SS2 +SS3

For more on Sums of Squares, see my video of that name: https://bit.ly/2JWMpoo .
For more on Sums of Squares within ANOVA, see my video, "ANOVA Part 2 (of 4): How It Does It: http://bit.ly/2nI7ScR .