We choose ‘7’ more than twice as often as other numbers.
Imagine you have to generate a random number from 1 to 10. That is an integer from 1 to 10 inclusive, with an equal chance (10%) of selecting each one. But, let’s say you have to do this without access to coins, computers, radioactive material, or other such access to traditional (pseudo) random number generators. All you have is a room of people.
The easy thing to do is to ask someone “Hey, pick a random number from 1 to 10!”. The person replies “7!”. Great! Now you have a number. However, you start to wonder, is the number uniformly random?
So you decide to ask a few more people. You continue to ask people and count their responses, rounding non-integers and ignoring answers from people who think that 1 to 10 includes 0. Eventually, you start to see that the pattern is not flat at all.