ANOM for Variances : What is this RMSE refering to ?

[#1]

RMSE is refering ??
How exactly RMSE is being calculated ?

RMSE = Sqrt [ Sum of Square (Predicted - Actual ) / N ]

If above formula , then what is predicted &  square?
==> predicted is variance of each group ?
==> actual overall variance ?

[#2]

The RMSE is available from the Summary of Fit table after using ANOVA command.

It is a pooled estimate of the within group variance, not the overall standard deviation. The latter estimate would include between group variation, too.

[#3]

Thank you for the explanation .