In Hypothesis Tests About P₁ - P₂, the Pooled Estimator $\bar { p } _ { 1 }$

In hypothesis tests about p₁ - p₂, the pooled estimator of p is a(n)

A) simple average of $\bar { p } _ { 1 }$ and $\bar { p } _ { 2 }$ .
B) weighted average of $\bar { p } _ { 1 }$ and $\bar { p } _ { 2 }$ .
C) geometric average of $\bar { p } _ { 1 }$ and $\bar { p } _ { 2 }$ .
D) exponential average of $\bar { p } _ { 1 }$ and $\bar { p } _ { 2 }$ .