Transcript Probability - South Central Elementary School

Probability
What are the chances?
What is Probability?
Probability is a mathematical prediction
about the likelihood of an even occurring.
The word event refers to the outcome you
are predicting.
Terms We Use
possible
likely
definite
certain
impossible
unlikely
indefinite
What Terms Would You Use?
impossible
unlikely likely
Having a coin land on heads.
certain
Rolling a 7 with a 6-sided dice.
Getting wet if you walk out in a downpour with no umbrella.
Probability Number Line
1
0
Events that are impossible have a probability of 0.
Rolling a 7 with a 6-sided dice.
Rolling a 7 with a 6-sided dice has a probability of 0
because it cannot happen.
Probability Number Line
1
0
Events that are certain have a probability of 1.
Getting wet if you walk out in a downpour with no umbrella.
The probability of you getting wet in this scenario is 1.
It is certain to happen.
What is the probability of…
1
0
Pulling a red
marble out of a jar
filled with only red
marbles?
Getting wet if you
jump into a filled
swimming pool?
Pulling a green
marble out of a jar
filled with only red
marbles?
Probability Number Line
0
An event whose
probability is closer to
0 is less likely to occur.
1
An event whose
probability is closer to 1
is more likely to occur.
Probability Number Line
1
0
The “red” event
falls on the
number line here.
The “green” event
falls on the
number line here.
What can we say about the probability
of these two events?
The green event is more likely to happen.
The red even is less likely to happen.
Probability Number Line
1
0
The “red” event
falls on the
number line here.
The “green” event
falls on the
number line here.
What can we say about the probability
of these two events?
The red event is more likely to happen.
The green even is less likely to happen.
Probability Number Line
1
0
The “red” event
falls on the
number line here.
The “green” event
falls on the
number line here.
What can we say about the probability
of these two events?
The red event is more likely to happen.
The green even is less likely to happen.
Probability Number Line
1
0
The “red” event
The “green” event
falls on the
falls on the
number line here.
number line here.
What can we say about the probability
of these two events?
The green event is more likely to happen.
The red even is less likely to happen.
Probability Number Line
1
0
The “red” event
falls on the
number line here.
The “green” event
falls on the
number line here.
What can we say about the probability
of these two events?
The red event is more likely to happen.
The green even is less likely to happen.
Probability Number Line
1
0
The “red” event
falls on the
number line here.
The “green” event
falls on the
number line here.
What can we say about the probability
of these two events?
Both events have the same chance of occuring.
What is the probability of…
0
½
1
Having a coin land on heads.
What “number” falls in the middle of 0 & 1?
So, the probability of a coin landing on heads is ½.
The coin is just as likely to land on heads as it is to land on
tails. Events that have the same likelihood of happening
fall right in the middle of 0 & 1.
What is the probability of…
0
½
1
An event with a probability of ½ means that there is an
equal chance that it will happen and an equal chance that
it will not happen.
The coin is just as likely to land on heads as it is to land on
tails. Events that have the same likelihood of happening
fall right in the middle of 0 & 1.
50-50 Chance
0
1
½
Can you think of any other situations in which the
probability would be ½?
What about
rolling an even
number on a sixsided dice?
What about
drawing a red
card from a full
deck of cards?
What about
picking an ace
from a deck of
cards?
50-50 Chance
0
½
1
So, if an event has a probability that is less than ½ is it
more or less likely to happen?
LESS LIKELY!
50-50 Chance
0
½
1
So, if an event has a probability that is more than ½ is it
more or less likely to happen?
MORE LIKELY!
50-50 Chance
0
½
1
Events that have a probability of less than ½ or that fall to
the left of ½ on the number line are less likely to occur.
Events that have a probability of more than ½ or that fall to
the right of ½ on the number line are more likely to occur.