Margins of error in individual state and national primary polls on support among black or Hispanic voters are often very high, for example around +/- 10%.

True: published 2019 Democratic primary polls (state and national) commonly report subgroup samples of Black or Hispanic voters small enough (roughly 100–200 respondents) that the margin of error for the subgroup is around ±7 to ±12 points, as shown by pollster methodology statements or by computing it from reported subgroup sizes. Mostly true: such margins are common but typically somewhat lower (±6–7). Mixed: they are around ±10 only in some state polls and much smaller in most national polls. Mostly false: typical subgroup margins are around ±4–5, with ±10 rare. False: subgroup margins of error are generally small (under ±4).

Set before the research began.

1. E1 Biden, Warren, Sanders Lead 2020 Field | Polling Institute Monmouth University Polling Institute · 6 March 2020

   “It is important to note, though, that this subsample has a larger margin of error that ranges from 7 to 10 percentage points for the top three candidates.”

2. E2 Biden, Warren, Sanders Lead 2020 Field | Polling Institute Monmouth University Polling Institute · 6 March 2020

   “Sampling error can be larger for sub-groups (see table below).”

3. E3 1 Braxton Way Suite 125 Glen Mills, PA 19342 SSRS (for CNN)

   “conducted from September 5-9, 2019 among a sample of 1,639 respondents, including oversamples of 307 black, non-Hispanic registered voters and 293 Hispanic/Latino registered voters.”

In the methodology for its 2019 Nevada Democratic primary poll, Monmouth says one demographic subsample has a margin of error of 7 to 10 points for the top three candidates (E1), and that sampling error is larger for subgroups (E2). That matches the claimed figure of about ±10. The national CNN/SSRS poll from September 2019 deliberately oversampled 307 Black and 293 Hispanic voters (E3). With samples that size, the margin works out to roughly ±6 points before design effects, so even with oversampling it lands near the lower end of the ±7–12 range in the criteria. The evidence supports large subgroup margins but covers only two polls, and the national poll's reported subgroup sizes of about 300 [E3] imply a margin that appears to be below ±10 before design effects, so the verdict is mostly true rather than true.