Probability Basics 75B98C
1. Let's start by understanding what probability is. Probability measures how likely an event is to happen. It is a number between 0 and 1, where 0 means the event will not happen and 1 means it will definitely happen.
2. The formula for probability of an event $E$ is:
$$P(E) = \frac{\text{Number of favorable outcomes}}{\text{Total number of possible outcomes}}$$
3. Important rules:
- The sum of probabilities of all possible outcomes of an experiment is 1.
- Probability of an impossible event is 0.
- Probability of a certain event is 1.
4. Example question a teacher might ask: "What is the probability of rolling a 3 on a fair six-sided die?"
5. Solution:
- Total possible outcomes when rolling a die = 6 (numbers 1 to 6).
- Favorable outcomes for rolling a 3 = 1 (only the number 3).
- Using the formula:
$$P(3) = \frac{1}{6}$$
6. Explanation: Since there is only one side with a 3 and six sides total, the chance of getting a 3 is one out of six.
7. Another common question: "What is the probability of getting an even number on a die?"
8. Solution:
- Even numbers on a die: 2, 4, 6 (3 favorable outcomes).
- Total outcomes: 6.
- Probability:
$$P(\text{even}) = \frac{3}{6} = \frac{1}{2}$$
9. This means there is a 50% chance to roll an even number.
10. Probability helps us predict outcomes in uncertain situations by quantifying likelihoods.