Question

A 2011 Gallup survey based on telephone and face-to-face interviews with 4,220 adults in China, aged 15 and older suggests that 30% smoke regularly or occasionally. The following is also noted "one can say with 95% confidence that the maximum margin of sampling error is 2.2 percentage points". Which of the following is true based on the results of this survey? 

• If we were to randomly sample another group of 4,220 Chinese adults we would find that exactly 30% of them smoke as well. 

• Exactly 30% of all Chinese adults smoke. 

• If the sample size was larger, the margin of error would be larger as well. 

• We are 95% confident that 25.6% to 34.4% of all Chinese adults smoke. 

• We are 95% confident that 27.8% to 32.2% of all Chinese adults smoke.

Answer 1

p hat = 30%

Margin of Error = 2.2%

CI = p hat +/- ME

CI = 30 % +/- 2.2%

CI = 27.8% , 32.2%

We are 95% confident that 27.8% to  32.2% of all chinese adults smoke.