So, after writing about David Cameron’s shoddy use of statistics in the Telegraph and now the margin of error in one YouGov poll that might just have changed the fate of the referendum and what happens after, I found myself thinking a lot about how official statistics and opinion polls are being used and reported in the media, and what pitfalls lie there.
Today, for instance, i want to talk about the “voodoo poll”, so called because it’s about as scientific as voodoo (and presumably because for the serious researcher seeing it reported as a serious poll in the media feels like a stab in the heart from a distance).
A “voodoo poll”, or open access poll, is one where a non-probability sample of participants self-select into participation.
In human language: sampling is the use of a subset of the population to represent the whole population. In probability sampling (random sampling), we have ways of calculating the probability of getting any particular sample, and therefore we can rigorously infer from the sample to the general population.In non-probability sampling, we do not; and therefore we need to use them with care.