I grew up with the idea that there are developed countries and developing countries. There was the ‘rich’ world and the 'poor’ world. I didn’t actively consider it, it’s just always been there. And it’s wrong.

Hans Rosling, in his excellent book Factfulness, shows that wealthier countries tend to have smaller families and a low child mortality rate, whereas poorer countries were more likely to have larger families and a high child mortality rate. Plotting the spread of countries in 1965 gives a reasonable approximation of a cluster of 'developed’ countries with small families where most children live, and 'developing’ countries with larger families where more children die. But that’s in 1965.

The world has changed a lot since then and now that model of dividing up the world into two buckets just doesn’t hold true with the data any more. Most people in the world are somewhere in the middle.

And more useful than dismantling my worldview is providing a new model to replace it with. A model with 4 income levels instead of 2 and the number of billions of people who currently live in each level. It’s a model with most people somewhere in the middle.

For more, check out the Factfulness book, or Gapminder. And you could do much worse than watch Hans’ entertaining TED talk: the best stats you’ve ever seen.

A world of 4 income levels

In my everyday life I’d have been hard pushed to put my finger on the difference between accuracy and precision but, in engineering at least, you learn that there is a clear difference between the two.

Precision describes how variable an outcome is, or how close repeated measurements or actions are to each other.

In contrast, something may be very precise but not be accurate to your intent or to the true value of a thing. That’s accuracy — how close you are to the true or intended value. If you’re hitting near your intended target then you’re accurate.

Hmm…one of those things where a sketchplanation works a whole lot better than words.

For the more spiritually inclined: Everything is aiming.

Or for the more statistically inclined: Measures of central tendency (mean, median, mode), and Common distributions (normal, skewed, pareto).

That accuracy is true to intention and precision true to itself I learned from Simon Winchester in Exactly: How precision engineers created the Modern World.

Accuracy and precision

Very easy to forget the difference between the mean, the median and the mode.

Median: the middle value of a list in ranked order.

Measures of central tendency: mean, median, mode

Normal (the weight of apples, measurement errors, IQ…), skewed (Number of children in a household, age at retirement…) and Pareto (80/20 rules, long-tails, size of meteorites).

Sketchplanations tagged with statistics