Question

Exhibit 8-1: A random sample of 1000 people was taken. Four hundred fifty of the people in the

sample favored Candidate A.

20. Refer to Exhibit 8-1. At 95% confidence, the margin of error is:

a. 0.0308

b. 0.0450

c. 0.4500

d. 450

Answer 1

Solution :

Given that,

n = 1000

x = 450

Point estimate = sample proportion = = x / n = 450/1000=0.45

1 -   = 1-0.45 =0.55

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 = 1.96   ( Using z table )

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

= 1.96 (((0.45*0.55) /1000 )

E= 0.0308

Margin of error = E =0.0308