Compared to what?

Jeanine MeyerMathematics/Computer Science & New

MediaNatural Sciences 3003

4 D's

• Definition

• Denominator (out of what), definition of denominator, absolute value

• Difference (compared to what, what's the difference)

• Distribution

Topics relating to voting

• Youth voting

– Claims for big increase for primaries for 2008

• Colbert Bump– Claims that appearing on the Comedy show

gives candidates 'a bump'

Comment• Predictions about voting done in terms of

demographics– Stereotypes: you are a certain gender, race, ethnicity,

age and so you will vote ….– Unfortunately, some truth to this but, not completely.– Microtargeting

• http://www.nytimes.com/2008/04/16/dining/16voters.html What's for Dinner? The Pollster Wants to Know

– Look at You Might Be …

– Keep in mind that the consultants [may] need something to say

Categories / Populations

• Assignment to categories may be problematic– Life is more complex

• Example: news story from August, 2007Women in their 20s out-earning Men in NYC (median 117%)

• Example: news reports (predictions) on voting in places like Florida

About women vs men

• Two populations• 53% of these women were college

graduates compared to 38% of men!!• In each category, men still out-earning

women– SIGH

• But…college educated women outearning men without college degrees AND there are more of them.

Florida

• Very complex situation– Older native residents versus 'snow birds'– Cubans versus other Latinos– North west (panhandle) versus specific

industries (space, Disneyworld,etc.) mid-state versus Miami versus …

• Western part of State is in different time zone. Polls close later!

US Time zones

How is something [actually] measured?

• Exit polls– Ask people leaving the polls (so it is pretty

definite they did vote) how they voted • Ask or guess demographics, issues• Extrapolate from voting district• Note: after the results are in, people tend to say

they voted with the winner.

• Federal Election Commission data– Legally required and available ($200 and up?)

Better

Not bad

Polling

• Pick a random sample of people (in the category to be studied)– Any person in the population equally likely to

be asked

• Ask them the question• Can make prediction about general

population, within …– Margin of error– Confidence level

Mathematics

• The distribution of the fractions of samples is more tightly distributed than the views of the general population.

• Still….it is possible to get a outlier (extreme) sample.

• Typical statement is: we are 95% confident that the actual result (say percentage of people saying they will vote X) is within the margin of error (this is a number they calculate, say 3-4 points) of our finding P.

Consider

• Flipping a fair coin many times – 100.

• Fraction of heads will be close to half – 50

• But you wouldn't be surprised if it was slightly off– 47, 48, 49, or 51, 52, …

• You would be surprised if it was way off– 80, 90??

• But this could happen!• Statistical analysis gives the margin of error and

the chances of it happening

Note for PA primary

• The polling results may be within margin of error.• The pollsters also should make assessment of

who will actually vote.– Most people don't vote, but many will not tell that to

the pollster.

• Many new registrations / switches• Most polls have been accurate, if the full

information is given. The news media sometimes mis-states information before and afterwards.

Youth voting

• Youth? – Typically, 18 to 30, but sometimes 17 to 24, 30…

• Historically, [very] low levels of voting• NOTE:

– historically, voting participation in USA is low across the age distribution compared to other places

– Primaries [much] worse than general elections– Off years much worse than presidential years

Gold standard of testing

• Double-blind

• Randomized

• Exact measurements, classifications

• Appropriate, adequate time intervals

Sometimes not possible!

What is the denominatorMeasure by dividing actual voting

Registered voters

Voter eligible population (this would not include people in jail, felons, illegal immigrants, people on the move)

Voter age population

http://elections.gmu.edu/Voter_Turnout_2008_Primaries.htm

Comparison to previous years?

Youth voting

In place of (youth voters) divided by (total youth population) or something similar

Youth vote versus total votingGives comparison (what's the difference) with 2004)

http://pewresearch.org/pubs/730/young-voters

Interpret results

• Chart does not say anything about turnout.

• These results COULD come about because older folks stayed home.

• In fact, 2008 primaries had record turnouts.– But youth increase was even more…..

Colbert Bump

James Fowler, UCSD, The Colbert Bump in Campaign Donations: More Truthful than Truthy,

http://jhfowler.ucsd.edu/colbert_bump.pdf• Appeared to be present for John Hall, successful

challenger for NY 19.– Colbert experience was very enjoyable for candidate,

staff and volunteers

• How to evaluate?– Can't arrange a double-blind test or cloning the

candidate and comparing

Selection bias

• Maybe candidates who agree to go on the show are better candidates

• Maybe candidates that are invited to go on the show are better candidates– Does Colbert want to boost specific

candidates?– Does Colbert want a good show?

Fowler approach

• Systematic procedure for identifying a match for each person that did appear on the Colbert show– Party (note: more Democrats than

Republicans)– Incumbency: compare incumbents with

incumbents, and challengers with challengers– Same or similar amount of funds raised at

time of appearance

Fowler approach continued

• Compare average number of donations and dollar amounts for time periods before and afterwards– Note: Use FEC data– Absolutely and also as

• Use statistical tests to evaluate significance of results

• This does not remove effects of selection bias, but indicates if there is a difference– Significant difference is one that is unlikely (say, less

than 1/20 of arising from chance)

Results

• Democrats yes!– Note: Democrats who chose to participate generally

were not doing as well– Advantage was at significant level

• Republicans no! – Appears to be opposite effect, but not statistically

significant– Note: Republicans who chose to participate generally

were doing well

Recommend

• Read paper—very clear, and funny

• Problem required (requires) inventive analysis

Predictions?

• Tomorrow in Pennsylvania– Results vs– Expectations

• "Buy on the rumor, sell on the news."

• Nomination

• Election

Summary

• Definition(s)

• Denominator

• What's the Difference– Compared to what

• Distribution