class: center, middle, inverse, title-slide # Questions about the Statistics + U.S. Elections ### Prof. Maria Tackett --- class: middle, center ### Who are some big names in prediction models? --- ### FiveThirtyEight <img src="img/fivethirtyeight.png" width="55%" style="display: block; margin: auto;" /> .center[ .small[Screenshot on Nov 2 of [FiveThirtyEight election forecasts](https://projects.fivethirtyeight.com/2020-election-forecast/?cid=rrpromo)]. ] Read more about their methodology [here](https://fivethirtyeight.com/features/how-fivethirtyeights-2020-presidential-forecast-works-and-whats-different-because-of-covid-19/). --- ### The Economist <img src="img/economist.png" width="55%" style="display: block; margin: auto;" /> .center[ .small[Screenshot on Nov 2 of [Economist election forecasts](https://projects.economist.com/us-2020-forecast/president)]. ] Read more about their methodology [here](https://projects.economist.com/us-2020-forecast/president/how-this-works). ] --- class: middle, center ### Are the polls taking into account the biases of the polling that caused issues 4 years ago? --- - There is little evidence of the "shy" Trump voter - Study by the [American Association for Public Opinion Research](https://www.aapor.org/Education-Resources/Reports/An-Evaluation-of-2016-Election-Polls-in-the-U-S.aspx) found that "interviewer administered polls did not under-estimate Trump’s support more than self-administered IVR (interactive voice response) and online surveys". -- - In 2016, many state-level polls underestimated the number of white voters without a four-year college degree. - Most polls have started weighting by education to reduce over-weighting of people with a college degree in the sample -- - In general, some groups of people are hard to reach, so pollsters have to apply statistical methods to re-weight their sample, i.e. make it more representative of the actual electorate (not just representative of who responds to a poll) --- ### Read more about sampling weights - [An Evaluation of 2016 Election Polls in the US](https://www.aapor.org/Education-Resources/Reports/An-Evaluation-of-2016-Election-Polls-in-the-U-S.aspx) by the American Association for Public Opinion Research - [Trump Supporters Aren’t ‘Shy,’ But Polls Could Still Be Missing Some Of Them](https://fivethirtyeight.com/features/trump-supporters-arent-shy-but-polls-could-still-be-missing-some-of-them/) by FiveThirtyEight - [A Resource for State Preelection Polling](https://www.pewresearch.org/methods/2020/08/18/a-resource-for-state-preelection-polling/) by Pew Research --- ### How statisticians think about predictions .pull-left[ ### Scenario 1 | | Predicted | Actual | Error | |-------------|-----------|---------|-------| | Candidate A | **51%** | 49.5% | -1.5% | | **Candidate B** | 49% | **50.5%** | +1.5% | **General consensus**: 😕 **Statistician**: 😄 ] -- .pull-right[ ### Scenario 2 | | Predicted | Actual | Error | |-------------|-----------|---------|-------| | **Candidate A** | **65%** | **55%** | -10% | | Candidate B | 35% | 45% | +10% | **General consensus**: 🙂 **Statistician**: 😱 ] --- ### What to consider when you look at models Models produce probabilities, not final answers! (Think about your logistic regression models.) - In 2016: FiveThirtyEight gave Trump a 30% chance to win the day before the election; the Upshot forecast gave him an 15% chance. - Rare events do happen! **March Madness** 🏀 - Is 15% or 30% really that rare? --- ## Are models accurate? But, the models weren't perfect... -- - In 2016, state polling errors were largely in the same direction - Clinton over-performed in a lot of blue states and under-performed in key Midwest states (**that's a problem! errors should be random**) -- - Issues with polling get baked into the model (bad data in, bad data out). -- - Some models didn't accurately account for correlation between states, especially in the Midwest. -- - Uncertainty was not effectively communicated to the general public --- ## Read more reflections on 2016 models - [An Evaluation of 2016 Election Polls in the US](https://www.aapor.org/Education-Resources/Reports/An-Evaluation-of-2016-Election-Polls-in-the-U-S.aspx) by the American Association for Public Opinion Research - [The Real Story of 2016](https://fivethirtyeight.com/features/the-real-story-of-2016/) by FiveThirtyEight - [Presidental Forecast Post- Mortem](https://www.nytimes.com/2016/11/16/upshot/presidential-forecast-postmortem.html#commentsContainer) by the Upshot --- ## Final thoughts - Focus on state polls, not national polls! -- - Don't read too much into early results - Can be potentially misleading based on who is expected to vote early, use mail-in voting, or vote on election day -- - There is a lot of uncertainty this year! -- - Don't let predictions affect your behavior! **VOTE!**