Use the Following Information for Questions:
a Comparison Is $p_1$

Use the following information for questions:
A comparison is to be made between the proportion of second graders that cannot read at second grade level and the proportion of third graders that cannot read at second grade level. School records from schools across the state are collected and records for 123 second graders and 146 third graders are randomly selected. Of the sampled second graders, 25 seem to be not reading at second grade level. Of the sample third graders, 26 do not read at second grade level.
-We know that if the sampling procedure were repeated, we would probably not observe 25/123 and 26/146 students who cannot read at second grade level again. What is the mean of the sampling distribution of the difference between the two proportions based on 123 second graders and 146 third graders?

A) $p_1$ - $p_2$
B) $\hat{p_1}$ - $\hat{p_2}$
C) 146 - 123
D) 0