{"id":2344,"date":"2016-10-13T15:53:23","date_gmt":"2016-10-13T20:53:23","guid":{"rendered":"http:\/\/blogs.ams.org\/blogonmathblogs\/?p=2344"},"modified":"2016-10-13T15:53:23","modified_gmt":"2016-10-13T20:53:23","slug":"how-polling-works-or-doesnt-work","status":"publish","type":"post","link":"https:\/\/blogs.ams.org\/blogonmathblogs\/2016\/10\/13\/how-polling-works-or-doesnt-work\/","title":{"rendered":"How Polling Works&#8230;Or Doesn&#8217;t Work"},"content":{"rendered":"<p>From the perpetual pit in my stomach, to the sleepless nights, to the eyes bloodshot from peering at endless forecast models and polling predictions, only one thing can be true: the election is nigh upon us.  In a time of uncertainty, where opinions and gut feelings seem to dominate, the mathematician in me craves the concreteness of numbers.  And polling does just that.  It gives me a quantified sense of what the future will look like.  And sure, it&#8217;s something cozy to wrap myself up in. But what do those numbers mean?  What am I really looking at when I see election forecasting?<br \/>\n<div id=\"attachment_2350\" style=\"width: 310px\" class=\"wp-caption alignright\"><a href=\"https:\/\/i0.wp.com\/blogs.ams.org\/blogonmathblogs\/files\/2016\/10\/PewPolls.png\"><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2350\" src=\"https:\/\/i0.wp.com\/blogs.ams.org\/blogonmathblogs\/files\/2016\/10\/PewPolls.png?resize=300%2C191\" alt=\"From the Pew Research Center assessment of the representatives of public opinion polls.\" width=\"300\" height=\"191\" class=\"size-medium wp-image-2350\" srcset=\"https:\/\/i0.wp.com\/blogs.ams.org\/blogonmathblogs\/files\/2016\/10\/PewPolls.png?resize=300%2C191&amp;ssl=1 300w, https:\/\/i0.wp.com\/blogs.ams.org\/blogonmathblogs\/files\/2016\/10\/PewPolls.png?w=417&amp;ssl=1 417w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><p id=\"caption-attachment-2350\" class=\"wp-caption-text\"><a \/>From the Pew Research Center assessment of the representatives of public opinion polls.<a><\/p><\/div><\/p>\n<p>First, there&#8217;s the question of the act of polling itself.  Like anytime you gather data for statistical analyses, <a href=\"https:\/\/www.scientificamerican.com\/article\/how-use-statistics-understand-poll-results\/\">there&#8217;s always a chance for sampling bias<\/a>.  Since it&#8217;s impossible to contact every single person in the country, pollsters need to find some representative subset.  That is, polls need to use <a href=\"http:\/\/www.quickanddirtytips.com\/education\/math\/how-to-use-statistics-to-understand-poll-results?page=1\">a small number of opinions to extrapolate the national opinion<\/a>.  National polls are typically conducted by phone, and <a href=\"http:\/\/www.people-press.org\/2012\/05\/15\/assessing-the-representativeness-of-public-opinion-surveys\/\">Pew Research reports<\/a> that &#8212; largely due to the disappearance of land lines over the past 20 years &#8212; response rates have gone from 36% in 1997 to 9% in 2012.  Since landlines can be autodialed while <a href=\"https:\/\/www.fcc.gov\/consumers\/guides\/wireless-phones-and-national-do-not-call-list\">cell phones must be dialed by hand<\/a>, calling land lines is still the best way to reach the largest swath of people as fast as possible.   <\/p>\n<p>This of course brings with it some problem of bias, since the set of all land line owners in the United States is a very particular demographic, not necessarily representative of the country as a whole.  But the Pew Research Center says that through careful <a href=\"http:\/\/www.pewresearch.org\/fact-tank\/2015\/07\/21\/the-challenges-of-polling-when-fewer-people-are-available-to-be-polled\/\">weighting of poll responses<\/a> they are able to overcome these biases. So a single poll, which already contains thousands of responses is weighted to correct biases and massaged to give the most accurate picture of national opinion.  <\/p>\n<p>But typically the poll results that you see on popular news sites don&#8217;t just reflect a single poll, they are often aggregates of the <a href=\"http:\/\/www.cnn.com\/election\">top 5 state and national polls<\/a> in some cases, to <a href=\"http:\/\/fivethirtyeight.com\/features\/a-users-guide-to-fivethirtyeights-2016-general-election-forecast\/\">several thousands of polls<\/a> in other cases.  And then the thousands of polls &#8212; <a href=\"http:\/\/projects.fivethirtyeight.com\/pollster-ratings\/\">some of which are more reliable than others<\/a> &#8212; are weighted to reflect their reliability, sample size, and representative regional demographics. <\/p>\n<p>And finally an aggregation of polls becomes and mathematical model when a few more factors are added into the mix.  Depending on the agency doing the modeling they will factor in effects like the <a href=\"https:\/\/en.wikipedia.org\/wiki\/Convention_bounce\">convention bounce<\/a>, the shape of the economy, and accuracy in prediction in certain states in past elections. All of these factors come together to build a <a href=\"https:\/\/youtu.be\/ioSEjNAJLQg\">robust<\/a> mathematical model to forecast the election. <\/p>\n<p>As one example, The New York Times maintains an active <a href=\"http:\/\/www.nytimes.com\/interactive\/2016\/upshot\/presidential-polls-forecast.html\">&#8220;Who Will Be President?&#8221; Scoreboard<\/a>, comparing their aggregate model will several of the other top forecasts like <a href=\"http:\/\/projects.fivethirtyeight.com\/2016-election-forecast\/\">fivethirtyeight<\/a>, <a href=\"http:\/\/elections.dailykos.com\/app\/elections\/2016\">Daily Kos<\/a>, <a href=\"http:\/\/elections.huffingtonpost.com\/2016\/forecast\/president\">HuffPost<\/a>, and <a href=\"http:\/\/election.princeton.edu\">Princeton Election Consortium<\/a>.  And to game things out even further they also have an <a href=\"http:\/\/www.nytimes.com\/interactive\/2016\/upshot\/presidential-polls-forecast.html#explore-paths\">interactive chart weighing out the probabilities<\/a> of each candidates path to the presidency based on electoral votes and states that have determined election outcomes in the past. <\/p>\n<p>And then there&#8217;s this dimly lit corner of election forecasting that doesn&#8217;t rely on polls at all.  These are places like the <a href=\"http:\/\/cookpolitical.com\/presidential\">Cook Political Report<\/a> which produces forecasts based more on reporting trends and expert opinions, or <a href=\"http:\/\/predictwise.com\/politics\/2016-president-winner\">PredictWise<\/a> which bases its forecasting on a combination of polls and betting markets.  <\/p>\n<p>There are a host of quantitative ways to deal with the election right now &#8212; and some slightly more <a href=\"https:\/\/terrytao.wordpress.com\/2016\/06\/04\/it-ought-to-be-common-knowledge-that-donald-trump-is-not-fit-for-the-presidency-of-the-united-states-of-america\/\">qualitative ways<\/a> <a href=\"http:\/\/www.scottaaronson.com\/blog\/?p=2777\">as well<\/a> &#8212; but I find the best thing to do is light some aromatherapy candles, immerse yourself in a warm bath of polls and forecasting, breathe deep cleansing breaths, and wait for November 8th.  <\/p>\n<div style=\"margin-top: 0px; margin-bottom: 0px;\" class=\"sharethis-inline-share-buttons\" ><\/div>","protected":false},"excerpt":{"rendered":"<p>From the perpetual pit in my stomach, to the sleepless nights, to the eyes bloodshot from peering at endless forecast models and polling predictions, only one thing can be true: the election is nigh upon us. In a time of &hellip; <a href=\"https:\/\/blogs.ams.org\/blogonmathblogs\/2016\/10\/13\/how-polling-works-or-doesnt-work\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n<div style=\"margin-top: 0px; margin-bottom: 0px;\" class=\"sharethis-inline-share-buttons\" data-url=https:\/\/blogs.ams.org\/blogonmathblogs\/2016\/10\/13\/how-polling-works-or-doesnt-work\/><\/div>\n","protected":false},"author":69,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[35,28,1],"tags":[630,628,629],"class_list":["post-2344","post","type-post","status-publish","format-standard","hentry","category-events","category-statistics","category-uncategorized","tag-election-forecasting","tag-mathematical-modeling","tag-polling"],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p3tW3N-BO","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/posts\/2344","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/users\/69"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/comments?post=2344"}],"version-history":[{"count":30,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/posts\/2344\/revisions"}],"predecessor-version":[{"id":2375,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/posts\/2344\/revisions\/2375"}],"wp:attachment":[{"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/media?parent=2344"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/categories?post=2344"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/tags?post=2344"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}