Question

When constructing a confidence interval for a population mean with σ known, the margin of error is E = zα/2 √σ n . If you want a confidence interval at the 80% confidence level, what is the value for zα/2?

Answer 1

Explanation

The margin of error is given by the formula

$E=Z_{\frac{\propto}{2}}\frac{\sigma}{\sqrt[]{n}}$

To get the value of

$\begin{gathered} Z_{\frac{\propto}{2}} \\ \text{from tables} \\ \end{gathered}$

The value is 1.28