ELI5: Explain Like I'm 5

Negative probability

Hey kiddo, do you know what probability is? It's when we try to figure out how likely or probable something is to happen. For example, if there are 5 red balls and 2 blue balls in a bag, the probability of picking a red ball is 5 out of 7 because there are a total of 7 balls.

Now, let's talk about negative probability. It's a little bit complicated, but I'll try to explain it in a way you can understand. Imagine you have a bag of 5 red balls and 2 blue balls like before. But this time, you take out one ball and put it back in the bag but you change the color to green. So now you have 5 red balls, 2 blue balls, and 1 green ball. If you add up the probabilities of picking each ball, it will equal 1, because you will definitely pick one of the balls.

But if you try to subtract the probability of picking a green ball from the total probability, you will get a negative number. That's because the green ball wasn't originally in the bag and you can't have a negative probability. Negative probability is when we imagine that something has happened that is impossible or didn't happen in reality, and then calculate the probability based on that imaginary situation.

In summary, negative probability is a concept we use when we imagine that something has happened that is impossible or didn't happen in reality, and then calculate the probability based on that imaginary situation. But we can't have a negative probability in real life.