~ Section 10.5 Notes ~
Experimental Probability
Determine the experimental probability of an event.
Use experimental probability to make predictions.
An experiment is an activity involving chance. Each repetition or observation of an experiment is a trial, and
each possible result is an outcome. The sample space of an experiment is the set of all possible outcomes.
Identify the sample space and the outcome shown for each experiment.
(a) Rolling a number cube
Sample space:
Outcome shown:
(b) Spinning a spinner
Sample space:
Outcome shown:
An event is an outcome or set of
outcomes in an experiment.
Probability is the measure of how
likely an event is to occur.
Probabilities are written as
fractions or decimals from 0 to 1,
or as percents from 0% to 100%.
Estimating the Likelihood of an Event
Write impossible, unlikely, as likely as not, likely, or certain to describe each event.
(a) A shoe selected from a pair of shoes fits the right foot.
(b) Katrina correctly guesses the last digit of a phone number.
(c) Max pulls a green marble from a bag of all green marbles.
(d) A randomly selected month contains the letter R.
You can estimate the probability of an event by performing an experiment.
The experimental probability of an event is the ratio of the number of times the event occurs to the number
of trials. The more trials performed, the more accurate the estimate will be.
experimental probability
=
You Try!
(a) An experiment consists of spinning a spinner.
Use the results in the table to find the experimental
probability that the Spinner does not land on green.
number of times the event occurs
number of trials
(b) An experiment consists of spinning a spinner.
Use the results in the table to find the experimental
probability that the Spinner lands on red.
You can use experimental probability to make predictions.
A prediction is an estimate or guess about something that has not yet happened.
For example:
Now you try!
A manufacturer inspects 1500 electric toothbrush motors and finds 1497 have no defects.
(a) What is the experimental probability that a motor chosen at random will have no defects?
(b) There are 35,000 motors in a warehouse. Predict the number of motors that are likely to have
no defects.
Guided Practice
1. Identify the sample space and the outcome shown for selecting a marble.
(a) Sample space:
(b) Outcome shown:
2. An experiment consists of spinning a spinner.
Use the results in the table to find the experimental probability of landing on blue.
3. The neighbors’ dog barked at Tana the last 4 out of 5 times she walked by their house.
(a) What is the experimental probability that the dog barks at Tana when she walks past the house?
(b) Predict the number of times the dog will bark at Tana if she walks past the house 45 times.