Question

Determine the critical value, zα/2 that corresponds to the given levels of confidence,

(a) (1 pt) 90%

(b) (1 pt) 96%

Answer 1

1) calculate critical value for 90% ci

Confidence level = 90%

= 1 - 0.9 = 0.10

Hence /2 = 0.10/2 = 0.05

We want to the area middle so

1 - 0.05 =.0.95

Look up the area 0.95 in the Z table

That is = 1.645

Critical value = 1.645

2)96%

Confidence level = 96%

= 1 - 0.96 =0.04

Hence /2 = 0.04/2 = 0.02

We want to the area middle so

1 - 0.02 = 0.98

Look up the area 0.98 in z table

Critical value = 2.05