A meta-analysis of Joe Biden's support in primary polls.

Update: This meta-analysis is no longer being updated, so "regularly updated" has been removed from the title of this post.

This post outlines the methods and results of a simple meta-analysis of the % support received by Joe Biden in national 2020 Democratic primary polls. Currently, the meta-analysis includes 125 polls, all national polls obtained from FiveThirtyEight's poll aggregator. The effect size is the % of the vote Biden gets in a given poll, and the sample size is just the number of people polled. These polls included a total of 324,920 people. The meta-analysis was carried out in keeping with the instructions outlined here.

Note that I have only ever added polls to this meta-analysis, with one exception: an open-ended ABC/WaPo poll that I removed because it had an unusually high percent of respondents (35%) who said they were undecided, which also resulted in all the candidates' percentages being significantly deflated.

Due to high heterogeneity (I2 = 94.8), a random-effects meta-analysis was performed, yielding an effect summary of 30.5% (95% CI 29.6% - 31.4%). No evidence was found that smaller-sample polls were biased in Biden's favor: on the contrary, there was a moderate positive correlation between sample size and % support for Biden (r = 0.36).