Download Probability: What Chance Do You Have?

Probability: What Chance Do
You Have?
Mrs. Gibson
Math 6
PROBABILITY
Definitions
Outcomes
Probability
Complex Probability
Odds
Samples of each
OUTCOMES
For any event or experiment, the end
result is called an outcome.
Probability
Probability is defined as a ratio comparing the
number of favorable or wanted outcomes to the
number of total possible outcomes.
Probability =
Number of wanted outcomes
Number of total possible outcomes
All probabilities are between 0 and 1 inclusive.
Complex Probability
Complex probability deals with multi-step
events. You find the individual
probabilities for each step or part of the
event first, then multiply those
probabilities to find the multi-step
probability.
Odds
The concept of odds are usually included
in the discussion of probability even
though the odds of an outcome are
different from the probability of the same
outcome.
There are two different types of odds:
Odds against an outcome
Odds in favor of an outcome
Both types of odds are defined as a ratio,
just like probability.
Odds against =
Number of unfavorable outcomes
Number of favorable outcomes
Odds in favor of =
Number of favorable outcomes
Number of unfavorable outcomes
There is a direct relationship between the
two types of odds.
Notice that the two types of odds are
reciprocals of each other.
Samples
Outcomes
You roll a die. The outcomes are:
Roll a one
Roll a two
Roll a three
Roll a four
Roll a five
Roll a six
Samples
(Simple) Probability
You use a deck of cards without jokers and
draw a card at random. The probability of
drawing a red card is 26/52 or ½ in lowest
terms.
Samples
Complex Probability
 You have a class with 5 boys and 8 girls. You draw a
student at random, and then pick a different student
at random next. The probability of choosing two girls
in a row would be found by multiplying the probability
of picking a girl the first time by the probability of
picking a girl the second time. 5/13 x4/12 = 5/39.
Samples
Odds
 If you are rolling a die the odds in favor of
rolling a six is 1 to 5 (1/5) while the odds
against rolling a six is 5 to 1 (5/1).
There are still many more topics in the
field of probability…permutations,
factorials, dependent vs. independent
multi-step events, and on and on.
Let’s go exploring!!!!!!