Question

Greatest president ~ A Gallup Poll of American adults in February 2009 asked the following question. "Which of the following presidents would you regard as the greatest: Washington, Franklin Roosevelt, Lincoln, Kennedy, or Reagan?" The order of the presidents was rotated to avoid bias. Based on the sample, a 95% confidence interval for the actual proportion American adults who choose Lincoln as the greatest is given by (0.1759, 0.2204).

What is the sample proportion? Give the exact answer as a decimal.

Answer 1

The sample proportion is 0.19815

Explanation:

A confidence interval has two bounds, a lower bound and an upper bound. The sample proportion is the halfway point between these two bounds, that is, the sum of the bounds divided by 2.

In this problem, we have that:

Lower bound: 0.1759

Upper bound: 0.2204

Sample proportion:

(0.1759 + 0.2204)/2 = 0.19815

The sample proportion is 0.19815