Question

In a random sample of 144 observations, pbar= 0.6.

a. With 95% confidence, what is the margin of error =

b. Critical value for the confidence interval

Answer 1

Solution :

n = 144

= 0.6

1 - = 1 -0.6 = 0.750

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 = 1.960

The critical value = 1.960

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

= 1.960 * (((0.6 * 0.4) /144)

= 0.080

Margin of error =0.080