# Confidence Interval on the Difference Between Proportions (2 of 4)

Therefore the proportions who solve the problem are 0.65 for the
psychology majors (p

_{1}) and 0.41 for the physics majors
(p

_{2}). The goal of the experiment is to estimate the
difference between the proportion of psychology majors in the

population that can solve the problem (π

_{1})
and the proportion of physics majors in the population that can solve it (
π

_{2}). The statistic
p

_{1} - p

_{2} is used as an estimate of π

_{1} -
π

_{2}. In this
experiment, the estimated value of π

_{1} - π

_{2} is
0.65 - 0.41 = 0.24.

To compute the confidence interval, the

standard
error of
p

_{1}- p

_{2} is needed. The standard error is:

The estimated standard error is:

= 0.067