Public Opinion Polling Chapter 6 AP Government

History of Polling George Gallup – surveyed citizens of Iowa in 1936, where his mother was running for public office Was able to predict the outcome of the election, but not to the degree of accuracy he desired His method of quota sampling called the race within 4 percentage points; so he switched to probability sampling

Quota v. Probability Sampling Quota sampling uses a quota that reflects the actual population – for example if you survey both sexes, the percentages would roughly be 52% female and 48% male. Probability sampling gives everyone an equal chance of being surveyed Gallup lowered his “margin of error” to +/- 2%.

Sample Size Statisticians have found that 384 is the magic number for many surveys. By doing a probability sample of 384, you margin of error will be +/- 5%. To lower your margin of error, you must increase sample size: 600 = +/-4%1067 = +/- 3% 2401 = +/- 2%9605 = +/- 1%

How do you decide upon sample size? For medical studies, your margin of error should ethically be in the 1-2% range – think of testing new medicines – you want to be VERY sure your results are accurate – it is literally a “matter of life or death” For public opinion polls – the margin of error of 3% seems to be standard. Some polls will go as high as 5%. Political opinion, though relevant, does not insist upon a small margin of error. How accurate do you want to be? How much money can you afford to spend? These questions will determine sample size for you. More participants = more money. Life or death = more money.

Famous Polling Organizations Gallup Poll - Pew - Quinnipiac - Ohio Poll - NBC/WSJ - Politics/_Today_Stories_Teases/Correct_NBCWSJ_poll.pdf Politics/_Today_Stories_Teases/Correct_NBCWSJ_poll.pdf