**All Probabilities Are Between 0 And 1**

- A probability of 1 means something is certain to happen

- A probability of 0 means something definitely won’t happen

- A probability of 0.5 means something is as likely to happen as it is not to happen

**If All Results Are As Likely To Happen Then You Can Use This Formula****Probability = Number Of Ways For Something To Happen / Number Of Possible Results****Example:** There are 8 balls in a bag. 3 are red. What is the probability of picking a red?

P(red) = 3/8 = 0.375**Probabilities Add Up To 1**

So P(event happens) + P(event doesn’t happen) = 1**Example:** A biased coin has a 0.7 chance of landing heads. What is the probability it will land tails?

P(tails) = 1 – P(heads) = 1 – 0.7 = 0.3