Answer
a. α = 0.05, two-tailed test
z =α/2 = 0.05/2 = 0.025
According to the table, $z_α$ = -1.96 and 1.96
b. α = 0.01, left-tailed test
According to the table, z = - 2.33
c. α = 0.005, right-tailed test
z = 1-α = 0.995
According to the table, z = 2.575
d. α = 0.01, right-tailed test
z = 1-α = 0.99
According to the table, z = 2.33
e.α = 0.05, left-tailed test
According to the table, z = - 1.645
