## What is Probability?

The measure of our belief that an event will happen.

So, how do we measure this belief?

- We watch and count.

Watch how often Gary rides down a certain hill and keep track of when he falls and when he doesn’t. Suppose he rode down the hill 100 times and fell 3 times. Then we could say that he fell 3 out of 100 times and the chance that he falls is `3/100` or 3%. - We can claim to have complete knowledge of a situation.

We all seem to believe that a quarter is fair when flipped, meaning that it is just a likely to land with heads facing up as tails. Since there is one head and two possible outcomes, then we could say that the chance of getting a head is `1/2` or 50%. - It could also be a wild ass guess.

There is a 50% chance that I will pass the test tomorrow. - Or maybe it is an educated guess

Random thoughts

probability, chance, likelyhood

fair

Dice, cards, coins, weather, sports

event, simple event, sample space

mutually exlusive

independent

odds

certainty, 1

uncertainty, 0

tree diagrams

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