What is Probability? Probability is a number from 0 to 1 that tells you how likely something is to happen.
Probability can be either theoretical or experimental.

Probability:

Probability THEORETICAL
Theoretical probability can be found without doing and experiment. EXPERIMENTAL
Experimental probability is found by repeating an experiment and observing the outcomes.

THEORETICAL PROBABILITY:

THEORETICAL PROBABILITY I have a quarter My quarter has a heads side and a tails side
Since my quarter has only 2 sides, there are only 2 possible outcomes when I flip it. It will either land on heads, or tails

THEORETICAL PROBABILITY:

THEORETICAL PROBABILITY When I flip my coin, the probability that my coin will land on heads is 1 in 2
What is the probability that my coin will land on tails??

Theoretical Probability:

Theoretical Probability Right!!! There is a 1 in 2 probability that my coin will land on tails!!!
A probability of 1 in 2 can be written in three ways:
As a fraction: ½
As a decimal: .50
As a percent: 50%

Theoretical probability:

Theoretical probability When I spin this spinner, I have a 1 in 4 chance of landing on the section with the red A in it.

A 1 in 4 chance can be written 3 ways::

A 1 in 4 chance can be written 3 ways: As a fraction: ¼
As a decimal: .25
As a percent: 25% Theoretical Probability

Theoretical Probability:

I am going to take 1 marble from the bag.
What is the probability that I will pick out a red marble? Theoretical Probability I have three marbles in a bag. 1 marble is red 1 marble is blue 1 marble is green

Theoretical Probability:

Theoretical Probability Since there are three marbles and only one is red, I have a 1 in 3 chance of picking out a red marble.
I can write this in three ways:
As a fraction: 1/3
As a decimal: .33
As a percent: 33%

Experimental Probability:

Experimental Probability Experimental probability is found by repeating an experiment and observing the outcomes.

Experimental Probability:

Experimental Probability Remember the bag of marbles?
The bag has only 1 red, 1 green, and 1 blue marble in it.
There are a total of 3 marbles in the bag.
Theoretical Probability says there is a 1 in 3 chance of selecting a red, a green or a blue marble.

Experimental Probability:

Experimental Probability Draw 1 marble from the bag. It is a red marble.
Record the outcome on the tally sheet

Experimental Probability:

Experimental Probability Put the red marble back in the bag and draw again.
This time your drew a green marble.
Record this outcome on the tally sheet.

Experimental Probability:

Experimental Probability Place the green marble back in the bag.
Continue drawing marbles and recording outcomes until you have drawn 6 times. (remember to place each marble back in the bag before drawing again.)

Experimental Probability:

Experimental Probability After 6 draws your chart will look similar to this.
Look at the red column.
Of our 6 draws, we selected a red marble 2 times.

Experimental Probability:

Experimental Probability The experimental probability of drawing a red marble was 2 in 6.
This can be expressed as a fraction: 2/6 or 1/3 a decimal : .33 or a percentage: 33%

Experimental Probability:

Experimental Probability Notice the Experimental Probability of drawing a red, blue or green marble.

Comparing Experimental and Theoretical Probability:

Comparing Experimental and Theoretical Probability Look at the chart at the right.
Is the experimental probability always the same as the theoretical probability?

Comparing Experimental and Theoretical Probability:

Comparing Experimental and Theoretical Probability In this experiment, the experimental and theoretical probabilities of selecting a red marble are equal.

Comparing Experimental and Theoretical Probability:

Comparing Experimental and Theoretical Probability The experimental probability of selecting a blue marble is less than the theoretical probability.
The experimental probability of selecting a green marble is greater than the theoretical probability.

Probability Review:

Probability Review Theoretical (can be found without doing an experiment)
Experimental (can be found by repeating an experiment and recording outcomes.) There are 2 types of probability: Probability is a number from 0 to 1 that tells you how likely something is to happen.

Probability Review:

Probability Review Probability can be expressed as a fraction, a decimal or a percentage.

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