Download Notes #12—Intro to Probability

Statistics and Probability
Chances, Probabilities and Odds Notes
Name: _______________________________________________
Date: _______________________________________________
There are three ways to express uncertainty. Each of the words represents a slightly different way to express the
likelihood of an event.
1. Chances:
2. Odds:
3. Probability:
Probability is the quantification of uncertainty. To understand what that means, we can start by formalizing the
notion of uncertainty. We will use the term random experiment to describe an activity or process whose
____________________________________________________.
Examples of random experiments: tossing a coin, rolling a pair of dice, drawing cards out of a deck of cards,
predicting the result of a game (football, basketball, etc.), or forecasting the path of a hurricane.
Sample space is the _______________________________________________________
For each example below, give the sample space (S) and the size of the sample space (N)
1. You are flipping a quarter one time.
S=
N=
2. You are flipping a quarter two times.
S=
N=
3. You roll a dice one time
S=
N=
4. You flip a coin 3 times, give the sample space for the number of times it lands on tails.
S=
N=
Finding the Probability of an Event
 Probability must be a fraction or a decimal between _______________________________
 A probability of 0 means…
 A probability of 1 means…
* To find the probability of an event happening, P( E ) 
Two events A and B are disjoint if they have no
outcomes in common. The probability that A or B
occurs is:
number of times an event can occur
size of your sample space
For two independent events A and B, the probability
that A and B occurs is:
Example: I have 10 blue poker chips, 15 red poker chips, and 20 white poker chips in a bag. What is…
1) The probability of pulling a white chip out of the bag?
2) The probability of pulling a blue chip out of the bag?
3) The probability of pulling a red chip out of the bag?
Dice: For this example, you are rolling a 6 sided dice one time.
1) What is the probability of rolling a 4?
2) What is the probability of rolling a 6?
Cards
1) What is the probability of drawing an ace?
2) What is the probability of drawing a red card?
3) What is the probability of drawing a spade?
4) What is the probability of drawing the Queen of Diamonds?
5) What is the probability of drawing a card greater than 10? (aces are high)
6) What is the probability of drawing a 6 or 7?
7) The person to your left draws an Ace of hearts. Without that person replacing their card, what is the probability
of you pulling one of the remaining aces?
8) What is the probability of drawing a King and a Queen on two successive draws without replacement?
9) What is the probability of NOT drawing a 4?