Calculating Simple Probabilities
Key Concepts
1. **Probability**: The likelihood of an event occurring, expressed as a number between 0 and 1.
2. **Sample Space**: The set of all possible outcomes of an experiment.
3. **Favorable Outcomes**: The outcomes that meet a specified condition.
4. **Formula**: The probability of an event \( P(E) \) is given by \( P(E) = \frac{\text{Number of favorable outcomes}}{\text{Total number of possible outcomes}} \).
Detailed Explanation
Probability
Probability is a measure of how likely an event is to occur. It is expressed as a number between 0 and 1, where 0 means the event will not occur, and 1 means the event will definitely occur. For example, the probability of rolling a 6 on a standard die is 1/6.
Sample Space
The sample space is the set of all possible outcomes of an experiment. For example, when rolling a die, the sample space is {1, 2, 3, 4, 5, 6}.
Favorable Outcomes
Favorable outcomes are the outcomes that meet a specified condition. For example, if the condition is rolling an even number on a die, the favorable outcomes are {2, 4, 6}.
Formula
The probability of an event \( P(E) \) is calculated using the formula:
\[ P(E) = \frac{\text{Number of favorable outcomes}}{\text{Total number of possible outcomes}} \]
Examples
Example 1: Calculate the probability of drawing a red card from a standard deck of 52 cards.
Solution: There are 26 red cards in a deck of 52. The probability is:
\[ P(\text{Red card}) = \frac{26}{52} = \frac{1}{2} \]
Example 2: Calculate the probability of rolling a 3 or a 4 on a standard die.
Solution: The favorable outcomes are {3, 4}. The probability is:
\[ P(\text{3 or 4}) = \frac{2}{6} = \frac{1}{3} \]
Analogies
Think of probability as the chance of picking a specific color from a bag of marbles. The sample space is all the marbles in the bag, and the favorable outcomes are the marbles of the specific color you are looking for. The formula helps you calculate the exact chance of picking that color.
Practical Application
Understanding simple probabilities is essential in various fields such as statistics, economics, and science. It helps in making informed decisions, predicting outcomes, and analyzing data effectively.