In the Context of a Two-Proportions Z-Test, Which of the Following

Multiple Choice

In the context of a two-proportions z-test, which of the following statements about the pooled sample proportion, $\hat { \mathrm { p } }$ , is/are true?
A. It estimates the common value of $p _ { 1 }$ and $p _ { 2 }$ under the assumption that the null hypothesis is true.
B. It is a parameter.
C. It is obtained by averaging the two sample proportions $\hat { p } _ { 1 }$ and $\hat { p } _ { 2 }$ .
D. It is equal to the proportion of successes in both samples combined.

A) B and D
B) $\mathrm { A }$ and D
C) $B$ and $C$
D) $\mathrm { A }$ and $\mathrm { C }$