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\textbf{A grocer would like to determine the proportion of milk cartons that have expired within 0.05 of the true proportion with a 95 percent confidence interval. What is the minimum required sample size?} 
Overseas Competition->Knowledge Point->Calculation Modules
\textbf{$n \geq (\frac{Z\_{\alpha/2}}{ME})^{2} {p(1-p)}$}  \textbf{Since p is unknown, then use p = ½. $n \geq (\frac{Z\_{\alpha/2}}{2ME})^{2}$}  \textbf{$Z\_{\alpha/2}=1.96$ The ME is how far off from the true proportion you are willing to be, in this case, 0.05}  \textbf{$n \geq (\frac{1.96}{2*0.05})^{2} = 384.16$ round up} 