Question

What are the z values for the following confidence intervals:

A) 99%

B) 95%

C) 90%

D) 80%

E) 70%

Please explain also so I can learn how you are doing it.

Answer 1

A)

Significnace level = 1 - 0.99 = 0.01

Z value at 99% confidence = Z/2 = Z_0.01/2 = Z_0.005

From Z table, Z value at 0.005 (That is 0.5% level) = 2.5758

B)

Significnace level = 1 - 0.95 = 0.05

Z value at 95% confidence = Z/2 = Z_0.05/2 = Z_0.025

From Z table, Z value at 0.025 (That is 2.5% level) = 1.96

C)

Significnace level = 1 - 0.90 = 0.10

Z value at 90% confidence = Z/2 = Z_0.10/2 = Z_0.05

From Z table, Z value at 0.05 (That is 5% level) = 1.6449

D)

Significnace level = 1 - 0.80 = 0.20

Z value at 99% confidence = Z/2 = Z_0.20/2 = Z_0.10

From Z table, Z value at 0.10 (That is 10% level) = 1.2816

E)

Significnace level = 1 - 0.70 = 0.30

Z value at 70% confidence = Z/2 = Z_0.30/2 = Z_0.15

From Z table, Z value at 0.15 (That is 15% level) = 1.0364