Critical z Values for Confidence Intervals
- Ann Defranco
This worksheet allows you to see how to compute critical z-values for confidence intervals. The middle section between the critical values is equal to the confidence level c and is bounded by the critical values. The shaded areas outside the middle section are equal to α = 1 - c, so each shaded area is equal to α/2. This worksheet can also be used to find critical z-values for two-tail hypothesis tests.
What do the values in green always sum to? As confidence level increases, what happens to the critical values? As confidence level increases, what happens to the width of the confidence level?