Question

What is the rejection region for a two tailed test when a=0.05?
a. [z] > 2.575
b. z>2.575
c. [z] > 1.96
d. [z]>1.645

Answer 1

A two-tailed test of a=0.05 is equivalent to two tests of a=0.05/2=0.025 for each for the upper and lower tails.

So for |z|>1.96 has a=0.025 (two tailed) is equivalent to z>1.96 and z<-1.96.

Ref:
http://www.math.unb.ca/~knight/utility/NormTble.htm