Therefore, if MSB is sufficiently larger than MSE, the null hypothesis can be rejected. If MSB is not sufficiently larger than MSE then the null hypothesis cannot be rejected. How much larger is "sufficiently" larger? That is determined by the statistical analysis explained in a later section.

The estimation of σ² by MSE in the analysis of variance is exactly the same as the estimation of σ²

For simplicity, assume that the sample sizes in each of the "a" samples are equal. The variance (σ²) is estimated by s² in each of the samples. The average of these "a" estimates of σ² is then used as an overall estimate of σ².