The Weighted Average of the Variances $S _ { 1 } ^ { 2 } \text { and } S _ { 2 } ^ { 2 }$

Essay

The weighted average of the variances $S _ { 1 } ^ { 2 } \text { and } S _ { 2 } ^ { 2 }$ of two independent samples is referred to as the __________ of $\sigma ^ { 2 }$ (the common variance of the two population variances), and is denoted by __________.