Probability
“What will Be?”
• The probability P, of an event
is the RATIO of successful
outcomes, called Successes, to
all outcomes of the event, called
Possibilities.
P(E)=
Number of outcomes favorable to the event
Total number of possible outcomes
BACK
• Probability of an
event is a Number
between 0 and 1.
BACK
CHANCE
• Chance is how likely it is that something
will happen. To state a chance, we use
a percent.
0
½
1
Probability
Certain not
to happen
Equally likely to
happen or not to happen
Certain to
happen
Chance
0%
50 %
100%
Likelihood
When the probability is greater than
0.5, implies the event is likely to
happen
When the probability is smaller than
0.5, implies the event is unlikely to
happen
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Applied Probability
What is the probability that
the sun will rise in the west
tomorrow?
Zero
The possible outcomes
Example 1: An unbiased coin
The total possible outcomes is head (H) or Tail (T)
1
P(H)=
2
and
1
P(T)=
2
BACK
Applied Probability
If you tossed a quarter 50
times, how many times
should it land on tails?
25 times
What is the Probability of Rolling a 5 or 6?
Total possible outcomes is 6.
P( 5 or 6 ) =
2 1
  0.33 3
6
3
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Probability
You Try
• A jar contains 12 blue ,
8 green, and 5 red marbles
–If you reach in & choose 1
–What is the P it is blue?
– What is the P it is not blue?
– What is the P it is not black?
BACK
Probability (Your Turn)
• What is the P it is blue?
P = 12/25 = .48
• What is the P it is not blue
P = 13/25 = .52
• What is the P it is not black
P = 25/25 = 1
BACK
Probability
“What will Be?”