Abstract:
In this paper, we investigate the calibration of public election polls. We present a definition of poll accuracy based on whether the poll’s margin of error spans the true election outcome. Most polls provide a 95% confidence interval along with the poll results, we sought to find whether their accuracy is as high as their confidence levels claim. Furthermore, we also wanted to see how this accuracy evolves over time as polls are conducted closer to the actual election. We find that even a week away from the election, polls claiming 95% confidence are only accurate 60% of the time. Moreover, we conclude that these polls would in fact need margins of error twice their reported width in order to be truly 95% confident. This provides a unique insight into the adjustment polls need over time and quantifies the systemic error polls contain beyond what the traditional statistics captures.
