Find a 95% Confidence Interval for the Difference Between the Proportions

Essay

Find a 95% confidence interval for the difference between the proportions of people who prefer cola versus root beer where $\hat { p } _ { \text {cola } }$
= .21, $\hat { p } _ { \text {root beer } }$
= .12,n_cola = 200,n_{root beer} = 150.