NOTES
Experimental and Theoretical
Probability
A little review first…
For questions 1-2, use the following spinner to find the probability:
1) P(3)
2) P(1 and even number)
1
2
4 3
4
5
4 3
For questions 3-4, use the following information to determine the probability of each event.
Then convert the probability to a percentage.
A bag contains 10 blue marbles, 5 red marbles, 4 green marbles, and 1 yellow marble.
3) P(red marble)
4) P(blue marble and yellow marble)
BIG IDEA #1: In science, in order to test a ______________, you perform an
____________________.
_______________________ probability is what we expect to happen (in THEORY);
to calculate theoretical probability, we use the probability formula
The probability formula: (simple events)
P(event) =
Number of favorable outcomes
Number of possible outcomes
_______________________ probability is what actually happens (in an “EXPERIMENT”);
 to calculate experimental probability, you have to do an experiment, survey, etc.
BIG IDEA #2: Theoretical is what _______________ happen. Experimental is what
______ happen!
Example: The table below shows the results of an experiment in which a coin is tossed.
Outcome
Heads
Tails
Tally
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Frequency
a) What is the theoretical probability of getting heads?
b) What is the experimental probability of getting heads?
You try!
1) A bag contains tiles with letters on them as follows: 4 A’s, 3 B’s, 2 C’s, 1 D. Tiles were
randomly drawn and the results are shown in the table below.
Outcome
A
B
C
D
Tally
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Frequency
a) What is the theoretical probability of pulling an A?
b) What is the experimental probability of pulling an A?
c) What is the theoretical probability of pulling a C?
d) What is the experimental probability of pulling a B?
e) What will happen as more trials are performed?
2) Andrea flips a coin 100 times.
a) How many times would you expect Andrea to get heads?
b) If she got tails 42% of the time, how many times did she actually get heads?
c) Determine whether a and b represent theoretical or experimental probability.