# Math Help - How to find zα/2 values for confidence interval

1. ## 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.

2. Start with the distribution for $\mu$, and the meaning of z?