Allocating Undecided Voters in Pre-election Polling

Abstract

Is there a way to make pre-election polls more accurate? This paper seeks to test some of the most popular methods of allocating ‘undecided’ voters, based on the underlying theory that the allocation of undecided voters will improve the public’s expectations of election results and a pollster’s claims about accuracy. Polling literature states the most popular methods to incorporate undecided voters include asking a “leaner” question that follows a ballot test question, or allocating the undecided proportionally to their vote preference. Both methods were used in this study, along with a third option in which an even-allocation, or essentially no allocation of undecided voters, took place. The study incorporates n=54 pre-election polls conducted in 20 different states, between October 26 and November 4, 2018, which were used to compare the three allocation methods. This includes an Absolute Error test (deviation between poll results and election results, Mosteller et al., 1949), a Statistical Accuracy test (absolute error compared with the poll’s margin of error, Kimball, 2017), and a Predictive Accuracy test (did the poll predict the actual election winner?). The study found no significant difference between the accuracy of the polls that included an allocation of undecided voters as compared to those that did not (χ2 (2, N=161)=.200, p=.905), suggesting that allocating undecided voters does not detract from, nor add to the reliability and validity of a pre-election poll.
 Keywords: undecided voter, pre-election polling, poll accuracy, allocation of undecided voter, political communication.