Question

A random sample of 803 people was taken. 154 of the people in the sample favored Candidate A. Find 90% confidence interval for the true proportion of people who favors Candidate A. Enter in the lower limit of the confidence interval you found.

Answer 1

Solution :

Given that,

Point estimate = sample proportion = = x / n = 154 / 803 = 0.192

1 - = 1 - 0.192 = 0.808

Z = 1.282

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

= 1.282 * (((0.192 * 0.808) / 803)

Margin of error = E = 0.018

A 90% lower confidence interval for population proportion p is ,

- E

0.192 - 0.018

0.174

Lower limit: 0.174