Probability - Statistics Study Guide

Understanding Probability

**Probability** is a measure of the likelihood that a given event will occur. The value of probability ranges from 0 (impossible event) to 1 (certain event).

Formula for Probability

The probability of an event is calculated using the formula:

Probability (P) = Number of favorable outcomes / Total number of possible outcomes

Example: Rolling a Die

Example 1: What is the probability of rolling a 3 on a fair six-sided die?

Step 1: Total number of possible outcomes = 6 (since the die has six sides).
Step 2: Number of favorable outcomes = 1 (only one side has a 3).
Step 3: Probability = 1/6 ≈ 0.167.

Example: Drawing a Card

Example 2: What is the probability of drawing a heart from a standard deck of 52 cards?

Step 1: Total number of possible outcomes = 52 (total number of cards).
Step 2: Number of favorable outcomes = 13 (since there are 13 hearts in a deck).
Step 3: Probability = 13/52 = 1/4 = 0.25.

Try It Yourself:

Calculate the probability of drawing a king from a standard deck of 52 playing cards.

Hint: There are 4 kings in the deck. Total number of cards = 52.

The formula is the same as in the examples above. Try calculating the probability!