# Sampling Distribution of the Difference Between Two Proportions (2 of 2)

Next chapter: Point
estimation
For this example, the mean of the sampling distribution of
p

_{1} - p

_{2} is:

μ= π

_{1} - π

_{2} =
0.8 - 0.4 = 0.4.

The standard error is:

= 0
.133.

The solution to the problem is the
probability that p

_{1} - p

_{2} is less than or equal
to 0. The number of standard deviations above the mean associated
with a difference in proportions of 0 is:

From

z table it can be determined that
only 0.0013 of the time would p

_{1} - p

_{2} be 3.01 or
more standard deviations below the mean.

Next chapter:
Point estimation