When we are comparing proportions, we are testing whether or not there is difference between populations.
When we write H0: p1 = p2, we are communicating that there is no difference between the proportions.
In other words, if I were to subtract these two proportions, I would get a value of 0. So, algebraically, p1 - p2 = 0.
Hence, any differences that are obtained in our sample values would be measured against 0.
What will the alternative hypothesis communicate if we write the following:
p1 < p2
p1 > p2
p1 <> p2 (not equal)?