Question

In March 2015, the Public Policy Institute of California (PPIC) surveyed 7,525 likely voters living in California. A strong majority of Californians support the president's executive order on immigration. The 90% confidence interval for the difference in proportions of Californians and all U.S. residents who support the executive order on immigration is (0.163, 0.196)

Which of the following conclusions about the confidence interval is most appropriate?

A. 90% of the time the difference in support between Californians and all U.S. residents for the executive order on immigration is between o.163 and o.196

B. There is a 90% chance that the difference in the proportions of Californians and all residents who support the executive order on immigration is between o.163 and o.196.

C. We are 90% confident that the difference in the proportions of Californians and all residents who support the executive order on immigration is between o.163 and o.196

Answer 1

C. We are 90% confident that the difference in the proportions of Californians and all residents who support the executive order on immigration is between 0.163 and 0.196

Explanation:

Confidence interval at the x% level, for a sample is between a and b.

Interpretation: We are x% sure that the true mean for the entire population is between a and b.

The 90% confidence interval for the difference in proportions of Californians and all U.S. residents who support the executive order on immigration is (0.163, 0.196)

So the correct interpretation is:

C. We are 90% confident that the difference in the proportions of Californians and all residents who support the executive order on immigration is between 0.163 and 0.196