This document provides an introduction to probability through a lecture given by Mr. Paik. It defines probability as a measure of how likely an event is to occur. Examples of probability are given as ratios, fractions, and percentages. The document explains that events with 0% probability are impossible, 100% probability are certain, and 50% probability have equal chances. It then discusses calculating probability as the number of ways an event can occur over the total number of outcomes. Coin flipping and dice rolling are used as examples. The document poses discussion questions and problems for students to practice applying probability concepts.

1. PROBABILITY
Lecture by: Mr. Paik

2. PROBABILITY
• Probability definition: Measure of how likely an event is to occur
• For example:
• Today, there is a 30% of rain.
• The odds of being struck by lightning are a million to one.
• What are some examples you can think of?

3. PROBABILITY
• Probability can be written as:
• A ratio such as 1:10
• A fraction such as 1/10
• A percentage such as 10%

4. PROBABILITY
• If an event is going to occur certainly, then the
probability of the event is 1 or 100%.
• If the event will NEVER happen, the probability will be
0% or 0.
• If the event may or may not occur at the same
probability, then the probability is .5 or 50%

5. Probability
Impossible Unlikely Equal Chances Likely Certain
0 0.5 1
0% 50% 100%
½

6. PROBABILITY
• Questions for thought!
• What are some events that have a probability of 0%?
• What are some events that have a probability of 100%?
• What are some events that have a probability of 50%?

7. Probability
P(event) = number of ways event can occur
total number of outcomes
• An outcome is a possible result of a probability
experiment
• When rolling a number cube, the possible
outcomes are 1, 2, 3, 4, 5, and 6

8. Probability
P(event) = number of ways event can occur
total number of outcomes
What is the probability of getting heads when
flipping a coin?
P(heads) = number of ways = 1 head on a coin = 1
total outcomes = 2 sides to a coin = 2
P(heads)= ½ = 0.5 = 50%

9. PROBABILITY Problem
• Martin woke up late and is now in a hurry to get to school. He
brushes his teeth, eats breakfast and now has to put on a pair of
socks. He opens his drawers and without looking, pulls out a pair of
socks. If in his drawer, he has 3 blue, 5 green, 2 red, and 6 white
socks, what are the chances of him grabbing red socks randomly?
P(event) = number of ways event can occur
total number of outcomes
• P(event)= 2/16=1/8, .125 or 12.5%

10. Discuss With Your Partners!
• If you roll a six sided cube with the numbers labeled 1-6, what is the
probability of rolling an odd number? How about an odd number
greater than 3?
• Odd numbers:1,3,5
• Total numbers: 1,2,3,4,5,6
• P(event)=3/6=1/2=50%
• Odd number greater than 3: 5
• Total numbers: 1,2,3,4,5,6
• P(event)=1/6

11. Probability
• Discuss with your partners and come up with fun, probability
questions that occur in your daily lives.
• Try to come up with an answer that is as accurate as possible.
• For example: If I have 150 songs in my ipod, what is the probability of
my favorite song playing when I put it on shuffle mode?
• Have fun!!

12. Bonus Question!
• Take a look at this video, and see if you are able to figure out the right
answer. Discuss with your group and let the teacher know what
conclusion you come to.
• https://www.youtube.com/watch?v=mhlc7peGlGg