Used to find sample size required for a given population and margin of error at 95% confidence level
z= z-score (we use 1.96 here for the 95% confidence level)
e= margin of error
p= at which proportion/percentage do we want the error that we've specified? Here we use 0.5 (50%), which is when the error is maximum. This results in the minimum required sample for a to give an error of maximum e
N= population size