How do you use variance analysis?

Answer 1

When data is homogeneous over k independent samples of size n_i for i=1,2,...,k, the pooled variance is given by

s_p^2=((n_1-1) s_1^2+(n_2-1) s_2^2+⋯(n_k-1) s_k^2)/(n_1+n_2+⋯+n_k-k)