Probability
Quantitative Aptitude – Probability
Study of chance: predicting how likely an event is to occur.
1. Basic Concept
\( P(E) = \frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}} \)
2. Types of Events
- Independent events: One doesn’t affect the other.
- Dependent events: Outcome affects next.
- Mutually exclusive: Only one can happen at a time.
3. Key Rules
- \( P(A') = 1 - P(A) \)
- If A and B are independent: \( P(A \cap B) = P(A) \cdot P(B) \)
- If A and B are mutually exclusive: \( P(A \cup B) = P(A) + P(B) \)
4. Examples
- Probability of drawing ace from a pack: \( P = \frac{4}{52} = \frac{1}{13} \)
- Probability of getting head on a coin toss: \( \frac{1}{2} \)
5. Tips for Exams
- Always list all outcomes for clarity.
- Check whether events are independent or mutually exclusive.
6. Mistakes to Avoid
- Counting overlapping outcomes multiple times.
- Confusing 'and' with 'or' scenarios.