Question

Which of the following is the upper critical value of z (z*) for an 80% confidence interval?

a. 1.96
b. .84
c. 2.33
d. 1.45
e. 1.28

Answer 1

Answer:

e. 1.28

Step-by-step explanation:

We have that to find our $\alpha$ level, that is the subtraction of 1 by the confidence interval divided by 2. So:

$\alpha = \frac{1-0.8}{2} = 0.1$

Now, we have to find z in the Ztable as such z has a pvalue of $1-\alpha$. This is our critical value.

So it is z with a pvalue of $1-0.1 = 0.9$, so $z = 1.28$

The correct answer is:

e. 1.28