ELI5: Explain Like I'm 5

Arithmetic-geometric mean

Imagine you have a bucket of candy and you want to share it equally with your friends. But, you don't just want to divide the candy, you also want to know what the "average candy" every person has.

When you divide the total number of candies by the number of friends, you get the arithmetic mean. For example, if you have 30 candies and you share it with 5 friends, each friend gets an arithmetic mean of 6 candies.

But what if you want to take into account the size of the candies? Some candies may be bigger than others, so the average size may not be the same for everyone. This is where the geometric mean comes in.

To find the geometric mean, you multiply all the candy sizes together and then take the nth root of the product, where n is the number of candies. For example, if your 30 candies are of different sizes, you could multiply them all together and take the 30th root to find the geometric mean.

The arithmetic-geometric mean is a combination of both the arithmetic and geometric means. It is a way to find a balance between the two. Instead of just taking the arithmetic mean or the geometric mean, you take the average of them.

To find the arithmetic-geometric mean, you start by taking the arithmetic mean of the first and second numbers. Then you take the geometric mean of those two numbers and replace the second number with the result. You keep doing this until you have one number left.

For example, let's say you have two numbers: 8 and 20.

- You start by finding the arithmetic mean: (8 + 20)/2 = 14
- Next, you find the geometric mean of 8 and 14: sqrt(8 x 14) = 10.6
- You then replace the second number with 10.6 and find the geometric mean of 10.6 and 20: sqrt(10.6 x 20) = 14.3
- You repeat this process until you have one number left: the arithmetic-geometric mean of 8 and 20 is 13.88

So, the arithmetic-geometric mean is a way to take into account both the size and quantity of the candies, and find a fair average for everyone.