This Monday, I’m featuring a very interesting and witty resource I discovered on Twitter: UKIP Maths are debunking affirmation made by UKIP members in their campaigns, and fighting them with cold hard facts.
Let’s look first at this graph; column on the left shows the Government’s estimates of the percentage of the UK population born overseas; the column on the right is from a 2013 ONS poll and shows the percentage of the UK population that respondents intending to vote UKIP at the next elections believe was born overseas.
(In case you’re wondering, the general public estimated the number of foreign-born people in the UK as higher than the actual figure, at around 25%; but UKIP supporters overestimate it by a wider margin).
So, UKIP supporters tend to think there are much more immigrants in the country than there actually are. Fair enough.
No way. Just… no way. There are many things I’ve been meaning to blog about for ages; things that are not David Cameron. But do I ever catch a break?
Turns out Sir Andrew Dilnot, chair of the UK Statistics Authority, has issued a letter refuting the Prime Minister’s claims yet again. This time, it is over his affirmation, in his Conservative Party conference speech, that Britain “is paying down its debts”.
Since I’ve been writing about statistics quite a bit (here and here), and since I happened to come across a really cute illustration on a blog in (I think?) Bosnian (yay for Google translate!), this week’s Stuff Explained Sunday will be about mean, median and mode.
So, we can see in this illustration how much each of these guys (individuals in the population) earned last month.
Now, we could say that the arithmetical average wage in the population is $5,700; with the variant “look, the average worker at my company earned $5,700 last month, can the union get off my back already??”. Which is arithmetically correct.
Except this gives us a very skewed view of how most individual guys in the picture are actually for themselves: only 4 people in the group are earning $5,700 or more, 20 are earning less, and a lot of those 20 quite a lot less.
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.