Answer:
1.28
Step-by-step explanation:
Given a confidence (c) = 0.80
α = 1 - c = 1 - 0.8 = 0.2
α/2 = 0.2/2 = 0.1
From the normal distribution table, The critical value necessary to form a confidence interval is gotten by getting the z value of α/2, which is the same as that of 0.4 (0.5 - 0.1). The z value of α/2 is:
[tex]z_\frac{\alpha}{2} =z_{0.01}=1.28[/tex]
