Here is the complete information requested to answer question 4. Please advise if you need any additional details.

4. (a) Voters will decide a statewide referendum soon and must vote either "Yes" or "No." You want to draw a sample and then compute the percentage that will vote "Yes." What is the size of the sample in order to be able to say the following: The probability is 95% that the true population percentage is equal to the sample percentage, plus or minus 2.5 percentage points.

(b) A news reader reporting the evening news, says "A random sample of 800 voters shows that 55% favor Candidate A over Candidate B with a margin of error of 3 percentage points." What piece of important piece of statistical information is missing from this statement?