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Opinion Polling as a “science”

Opinion Polling as a “science” - sampling methods cell phone/caller ID impact “statistical magic” of polls margin of error… response rates? Internet polling industry reporting standard Key terms: population : the group you want to know about

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Opinion Polling as a “science”

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  1. Opinion Pollingas a “science” • - sampling methods • cell phone/caller ID impact • “statistical magic” of polls • margin of error… • response rates? • Internet polling • industry reporting standard

  2. Key terms: population: the group you want to know about sample: the subset of the population surveyed estimate: your predicted % for any question… EX: Obama has 55% support in Indiana margin of error: +/- __% [a range around the estimate, usually at confidence level of 95%...] EX: Obama at 55% +/- 3%, so we are 95% sure Obama is betw. 52% & 58%

  3. SAMPLING methods: SRS: random (every person in population has an equal chance of inclusion/selection) Stratified: divide into characteristics’ subsets (ex = race), then sample within each Cluster: often multistage, based on sampling geographic areas [county, city, blocks…] Our Simpson Survey = a “list-based” survey, closer in some ways to the U.S. census

  4. Impact of Cell Phones / Caller ID • …increasingly an issue • “Cell phone only” use associated w/ youth • Caller ID allows more screening of calls… • To the extent youth don’t vote in high %s and the target of many surveys is voting, it alleviates the problem (sadly…) • EITHER one of them is a problem IF there are systematic differences between the people who participate and those who do not answer…

  5. “Statistical Magic of Polling” …“coin flip” example Exercise: FIND me the latest Obama/Hillary poll results… …the “soup” analogy

  6. Margin of Error… …increase in sample size [decrease in Margin of Error] must be balanced with rising $$$ cost of contacting more respondents!!!

  7. RESPONSE RATES • …increasingly an issue • range between 30 and 40% of all attempts • again, it becomes a big problem IF there’s a systematic difference between “Y” and “N”… • - pollsters make multiple attempts to “hit” (re-contact) #s to raise the response rate • - problem is BIG for instant response poll; for example, overnight polls the day after the presidential debates!

  8. INTERNET / ONLINE POLLS …some credible; MOST are NOT! [pseudopolls] CREDIBLE: * use of a pre-recruited panel carefully selected to represent the “population” of interest [Harris Interactive], OR the full U.S. population [Knowledge Networks] Example = http://news.yahoo.com/polls

  9. INDUSTRY Reporting Standards NCPP standards: You MUST report… (1) sponsor of poll (2) dates of interviews (3) interview/contact method (4) population of interest (5) the “N” (sample size) (6) margin of error (+/- __%, 95% conf.) (7) LINK to full questions to see wording

  10. ONLINE EXERCISE: Scavenger hunt: FIND 3 ex. of news media-reported poll results, and then APPLY the 7 reporting rules… GRADE their disclosure from an “A” to an “F” …how well do they inform citizens about the methods?

  11. QUESTIONS ?

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