Probability

Lesson 7 (4th 6 Weeks) TEKS 6.9B

Probability

How likely it is that a particular outcome will occur

A number from 0 through 1

Can be written as a fraction, decimal or a percent

Certain Event

Probability of 1 or 100%

Impossible Event

Probability of 0 or 0%

Probability written as a fraction

Numerator is the number of favorable outcomes for the experiment or eventDenominator is the number of ALL possible outcomes for the experiment or event# of favorable

outcomesTotal # of possible outcomes

P(outcome)

=

Compliment of an event

All possible outcomes that are NOT favorable.

The sum of the probability of an event and its compliment is 1.EX: P(red tile) = 1/3

P(not red tile) = 2/3 P(red) + P(not red) = 1/3+2/3 = 3/3 or 1

Example:

The candy bowl has 10 Snickers, 3 Butterfingers, 7 Reese's, and 5 Babyruths. If you choose one at random, what is the probability that the candy you select will be a Snickers?

First let’s add up how many total pieces of candy there are.

10375+

25

25

Now let’s write the probability as a fraction.

10

÷We can simplify this fraction.

2510 5

525=

At Pine Ridge Elementary School, 1 out of 10 of the students can’t swim. If a student is chosen at random from the school, what is the probability that the student knows how to swim?

At Pine Ridge Elementary School, 1 out of 10 of the students can’t swim. If a student is chosen at random from the school, what is the probability that the student knows how to swim?

If 10 kids were surveyed and 1 said they can’t swim, that means the other kids must be able to swim.

10 – 1 = 9 can swim10

9