Question

how do I express the confidence interval (0.061,0.117) in the form of (p - E < p < p + E).

Answer 1

upper - lower / 2 = E
p = (upper + lower)/2

Answer 2

that's (upper-lower)/2 = E, of course

Answer 3

Miscalculated the average, sorry.
\[p=\frac{0.117\color{red}{+}0.061}{2}=\color{red}{0.089}\]

Answer 4

How do I find E?

Answer 5

Solve this system:
\[\begin{cases}
0.089+\epsilon=0.117\\
0.089-\epsilon=0.061
\end{cases}\]
You need only solve for one of these equations, since either will give you the same \(\epsilon\).