## Elementary Statistics (12th Edition)

$\alpha=1-0.99=0.01.$ Using the table: $z_{\alpha/2}=z_{0.005}=2.58.$ Hence the sample size:$\left (\frac{z_{\alpha/2}\cdot \sigma}{E}\right)^2=\left (\frac{2.58\cdot 0.79}{0.2}\right)^2\approx104$.It doesn't make sense to collect samples at your college, because then it becomes a convenience sample and hence cannot be generalized.