4.3 Experimental & Theoretical Probability

What is Probability?The probability of an event is how

likely it is to occur.Always a number between 0 and 1.Probability of 1:

event will definitely occur.Probability of 0:

event will never occur.

Theoretical ProbabilityThe theoretical probability that an

event A will occur is:

Can be expressed as a fraction, decimal, or %.

Experimental ProbabilityExperimental probability is found

using an experiment, survey, or history of the event.

Found using:

ExampleSam rolled a die 50 times.

A 3 appeared 10 times.What is the experimental probability

of rolling a 3?

What is the theoretical probability?

ExampleA coin is tossed 60 times. Heads

appeared 27 times. Find the experimental probability of

flipping heads.

What is the theoretical probability?

Example:In 1998, a survey asked internet

users for their ages. Find the exp. probability that a randomly selected internet user is:

at most 20 years old?

at least 41 years old?

Age # of users

Under 21 1636

21 -40 6617

41 – 60 3693

61 – 80 491

Over 80 6

You Try!Using the table, what was the

experimental probability of an even number being rolled?

What is the theoretical probability?