What are non-independent events?

Non-independent events are like best friends who always know what the other is going to do next.

Imagine you have a bag full of red and blue marbles. If you pick one marble without looking, that’s one event. Now, if you don’t put that first marble back in the bag before picking another one, then the second pick depends on the first, they’re non-independent events.

Let’s say there are 5 red marbles and 5 blue marbles. You pull out a red marble first, now there are only 4 red marbles left. That means your chance of picking another red marble is smaller than before. The second pick isn’t random anymore; it's connected to the first one.

But if you had put the first marble back in, then both picks would be independent events, like rolling a die twice, each roll doesn’t care about the last one.