Answer
$z_0\lt z_{\frac{α}{2}}$: null hypothesis is not rejected.
There is not enough evidence to conclude that the proportion of successes with cream A is different from cream B.
Work Step by Step
$H_0:~p_1=p_2$ versus $H_1:~p_1\ne p_2$
$z_0=\frac{|f_{12}-f_{21}|-1}{\sqrt {f_{12}+f_{21}}}=\frac{|9-13|-1}{\sqrt {9+13}}=0.64$
$z_{\frac{α}{2}}=z_{0.025}$
If the area of the standard normal curve to the right of $z_{0.025}$ is 0.025, then the area of the standard normal curve to the left of $z_{0.025}$ is $1−0.025=0.975$
According to Table V, the z-score which gives the closest value to 0.975 is 1.96.
Since $z_0\lt z_{\frac{α}{2}}$, we do not reject the null hypothesis.
