Chapter 9 - Section 9.1 - Assess Your Understanding - Applying the Concepts - Page 438: 38c

In part (a), we used $p ̂ =0.55$. In part (b), since no prior estimate is available, we are forced to use $p ̂ =0.5$. But, both values are very close and, since $z_{\frac{α}{2}}$ and $E$ are the same, the results are very close.

(a): $p ̂ =0.55$, $z_{\frac{α}{2}}=1.645$ and $E=0.04$ (b): $p ̂ =0.5$, $z_{\frac{α}{2}}=1.645$ and $E=0.04$