The rule of 5

“We must become more comfortable with probability and uncertainty.” ~ Nate Silver

If you told me that your processing team turned around over a thousand widgets per day and that you just asked five people how long their last widget took to process: 28, 36, 24, 30 and 31 minutes. Now if I say that I predict your median process time is somewhere between 24 and 36 minutes you will probably think that’s a reasonable guess based on the few examples. However, if I then said I was over 93% sure of my prediction, you might think I was being rather over confident. Lets look at the maths behind why I can be so sure with so few data points.

Continue reading

How many Countries in Africa?

“The scientist is not a person who gives the right answers, he’s one who asks the right questions.” ~ Claude Lévi-Strauss

If you don’t know the answer to the question in the title then you’re far from alone –please don’t google it just yet!

So, imagine you’re observing a study. There are two groups that are separately given the same task, to collectively decide whether the number of countries in Africa is more or less than a certain provided value. One group are asked “Are there more or less than 20 countries?” for the other group the provided number is 40. Lets look at how this is done and how the groups differed.

Continue reading