Solution :
a). The point estimate of proportion of college graduates among women who work at home,
[tex]$\hat p =\frac{166}{506}$[/tex]
= 0.3281
99.5% confidence interval
[tex]$=\left( \hat p \pm Z_{0.005/2} \sqrt{\frac{\hat p (1- \hat p)}{n}} \right)$[/tex]
[tex]$=\left( 0.3281 \pm 2.81 \sqrt{\frac{0.3281 \times (1- 0.3281)}{506}} \right)$[/tex]
[tex]$=(0.3281 \pm 0.0586)$[/tex]
[tex]$=(0.2695, 0.3867)$[/tex]