Download Basic Probability Lesson

Probability
OBJECTIVE
Find the probability of a simple event.
Differentiate between theoretical and
experimental probability.
Vocabulary
experiment
trial
outcome
sample space
event
probability
impossible
certain
An experiment is an activity in which results
are observed. Each observation is called a trial,
and each result is called an outcome. The
sample space is the set of all possible
outcomes of an experiment.
Experiment
Sample Space
flipping a coin
heads, tails
rolling a number cube
1, 2, 3, 4, 5, 6
guessing the number of
jelly beans in a jar
whole numbers
An event is any set of one or more outcomes.
The probability of an event, written P(event),
is a number from 0 (or 0%) to 1 (or 100%) that
tells you how likely the event is to happen.
• A probability of 0 means the event is
impossible, or can never happen.
• A probability of 1 means the event is certain,
or has to happen.
• The probabilities of all the outcomes in the
sample space add up to 1.
Impossible
Equally likely
as unlikely
Certain
1
2
3
4
1
0
1
4
0.25
0.5
0.75
1
0%
25%
50%
75%
100%
0
• Experimental Probability – the likelihood
that an event will occur based on data that
has been collected.
P(event) =
• Theoretical Probability – the likelihood
that an event will occur based on what
should happen or theory.
P(event) =
1
2
3
4
5
6
7
8
9
10
Coin 1
H
H
H
H
T
H
T
T
H
T
Coin 2
T
H
H
T
T
H
T
T
T
H
Trial
1) What is the probability that both coins came up the same?
2) What is the probability that both coins come up heads?
3) What is the probability that at least one coins is heads?
4) What is the probability that neither coin is heads?
5) If I flip the 2 coins 60 times, how many times would you
expect the result to be 2 heads?
You draw a card from a standard deck of
playing cards,
1) What is the probability that you draw a king?
2) What is the probability that you draw a red card?
3) What is the probability that you draw a club ?
4) What is the probability that you draw the jack of hearts?
Possible Outcomes of 2 Number
Cubes
1-1
2-1
3-1
4-1
5-1
6-1
1-2
2-2
3-2
4-2
5-2
6-2
1-3
2-3
3-3
4-3
5-3
6-3
1-4
2-4
3-4
4-4
5-4
6-4
1-5
2-5
3-5
4-5
5-5
6-5
1-6
2-6
3-6
4-6
5-6
6-6
36
2
3
4
5
6
7
8
9
10 11
12
6-1
5-1 5-2
4-1 4-2 4-3
3-1 3-2 3-3 3-4
2-1 2-2 2-3 2-4 2-5
5-3
4-4 4-5
3-5 3-6
2-6 4-5
4-6
5-5
6-5
1-1 1-2 1-3 1-4 1-5 1-6 2-6 3-6
4-6
5-6
6-6
2
10 11
12
1/36
1/36
% 2.8
3
4
5
6
7
8
9
2/36 3/36 4/36 5/36 6/36 5/36 4/36 3/36
1/18 1/12 1/9 5/36 1/6 5/36 1/9 1/12
5.6
8.3
11.1 13.9 16.7
13.9
11.1
8.3
2/36
1/18
1/36
1/36
5.6
2.8
P(2)
10 Rolls
50 Rolls
100 Rolls
P(7)
P(10)