Question

How do I calculate a and z a/2?

Answer 1

Given a confidence interval of 95% :

• $\alpha = 1 - 0.95 = 0.05$
• $z_{\alpha/2} = z_{0.05 / 2} = z_{0.025} = 1.96$

Given a confidence interval of 99%:

• a = 1 - 0.99 = 0.01
• z a/2 = 0.01 / 2 = z 0.005 = 2.576