At issue is the proportion of people in a particular county who do not have health care insurance coverage. A simple random sample of 240 people was asked if they have insurance coverage, and 66 replied that they did not have coverage. Based on these sample data, determine the 95% confidence interval estimate for the population proportion.
A) (0.239, 0.321)
B) (0.259, 0.301)
C) (0.224, 0.336)
D) (0.268, 0.292)

Question

Quizplus · Accepted Answer

The sample proportion is 66/240 = 0.275. The standard error is calculated as sqrt[(0.275)(1-0.275)/240]. Using a Z-score of 1.96 for a 95% confidence interval, the margin of error is 1.96 * standard error. The confidence interval is then 0.275 ± margin of error, which matches choice C.

At Issue Is the Proportion of People in a Particular