In public health, we rely heavily on samples, as measuring everyone you are interested is often impractical. However, this requires a lot of thought and development in order to avoid unintentionally biasing your sample, as was the case for the USC Dornslife/LA Times Daybreak poll.
Last week, a story came out about how one 19-year old black man in Illinois was single-handedly changing the standings of the US Presidential election. This was based on the results from the USC Dornsife/Los Angeles Times Daybreak, a survey of voter attitudes on “a wide range of political, policy, social and cultural issues.” In this survey, Donald Trump has generally held the lead, until last week, when Hillary Clinton came out in front. Interestingly, this is markedly different than most other national polls, that have shown Clinton is generally ahead, or a much closer contest than that poll would have you believe. So what happened?