# How to find zα/2 values for confidence interval

• February 17th 2011, 11:13 AM
jhallett17
How to find zα/2 values for confidence interval
Suppose we have a large sample of n = 400, we happen to know σ, and we use
mean + 1.43(stnd. dev./square root of n)
to obtain a confidence interval for μ.

What is the appropriate zα/2 value for a 45.8% confidence interval?

This question is causing me problems as I am just not really sure where to start with it.
• February 17th 2011, 05:06 PM
Volga
Start with the distribution for $\mu$, and the meaning of z?