What is the difference between event of 0 probability and null event I can't understand the difference between Null event and an event that has 0 probability.
In the Null event the event which no way could happen?
and is the event of 0 probability the event that can happen but which would not happen in certain circumstances?
Is the event that has 0 probability a Null event? or can an event ot bu null but have 0 probability?
I also want to discuss this example: I have a circle and I inscribe a triangle in it. There are 3 cases where it could be straight angle triangle(one angle is 90 degrees) but the probability of it is 0. Why is it like that?
Please provide external links if available
Thanks
 A: A null event is simply an event that cannot happen, or at least is outside of the space you're concerned with taking the probabilities of.
A rather trivial example: if I have 6 apples and 14 oranges and you pick one, what is the probability it's a banana? Sure, it's zero, but why? It's because it's a null event, in the sense that it wouldn't be possible for you to pick a banana to begin with.
Yet you can have events that are possible, yet have 0 probability. Consider, continuing my fruit example: infinitely many times, you pick a fruit at random, then give it back to me. What is the probability they're all apples? Well, the probability each time is $6/20 = 3/10$, and then these multiply: so what you're really asking is, what is the limit of $(3/10)^n$ as $n \rightarrow \infty$? Clearly that's zero. It's possible - but in terms of probability, it has zero probability.
It's kind of like the whole "all fingers are thumbs but not all thumbs are fingers" thing. All null events have zero probability, but not all events of zero probability are null events. What distinguishes them is essentially whether they can happen.
