You are watching a nightly news broadcast on CNN and the rep

You are watching a nightly news broadcast on CNN and the reporter says that a 90% confidence interval for the proportion of Americans who supported going to war in Iraq was ( 0.4426 , 0.5007 ). You also note that the footnote says this is based on a random sample performed by Gallup with 793 respondents. What is the correct interpretation of this confidence interval?

a) We are 90% confident that the proportion of all Americans who supported going to war in Iraq is between 0.4426 and 0.5007.

b) We are 90% confident that the proportion of all Americans surveyed who supported going to war in Iraq is between 0.4426 and 0.5007.

c) We are certain that 90% of Americans will be between 0.4426 and 0.5007.

d) We are 90% confident that of the 793 repspondents, between 0.4426 and 0.5007 of them supported the decision to go to war.

e) We cannot determine the proper interpretation of this interval.

Solution

a) We are 90% confident that the proportion of all Americans who supported going to war in Iraq is between 0.4426 and 0.5007.