Question

Give the value of zα2 for a 94% confidence interval for a population proportion generated from a sample of size n = 125 with a sample proportion value of p¯ = 0.715.

Answer 1

Solution :

Given that,

Point estimate = sample proportion = = 0.715

1 -   = 1- 0.715 =0.285

At 94% confidence level the z is ,

Z/2 = 1.881   ( Using z table )

Margin of error = E = Z/2   * ((( * (1 - )) / n)

= 1.881 (((0.715*0.285) /125 )

E = 0.076

A 95% confidence interval for population proportion p is ,

- E < p < + E

0.715 - 0.076 < p < 0.715 +0.076

0.639< p < 0.791