11– 2 Probability
Definitions:
experimental probability: when the data is gathered from observation. Each
observation is called an experiment or trial.
***The more trials you conduct when doing experimental probability the closer an
closer your probability solutions will get to the true theoretical probability values! (ie.
the more accurate/reliable your experimental data will become)
sample space: the set of all possible outcomes to an experiment or activity.
equally likely outcomes: when each outcome in a sample space has the same chance
of occurring. (Random Outcomes)
theoretical probability: if a sample space has n equally likely outcomes and the
specific event that you are looking for occurs in m of these outcomes, then the
theoretical probability is P =
m
n
Odds: the ratio of the favorable outcomes to the unfavorable outcomes. Always leave
an odds answer as a simplified fraction!
Experimental Probability Formula
Algebra 2: Lesson 11-2 Probability
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Example 1: Find the probability of each.
a. A softball player got a hit in 20 of her last 50 times at bat. What is the experimental
probability that she will get a hit in her next at bat?
b. A student got 35 of the last 45 questions correct on the exam. What is the
experimental probability that he will get the next question on the exam correct?
c. A basketball player attempted 24 shots and made 13. Find the experimental
probability that the player will miss the next shot she attempts.
Algebra 2: Lesson 11-2 Probability
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Example 2: A bucket contains 15 blue pens, 35 black pens, and 40 red pens. You pick
one pen at random. Find each theoretical probability.
a. P(black)
b. P(blue or red)
c. P(not blue)
d. P(black or not red)
Algebra 2: Lesson 11-2 Probability
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Example 3: You roll 2 standard number cubes. Find each theoretical probability.
a. P(5)
b. P(11)
c. P(sum is less than 4)
d. P(8 or 2)
Algebra 2: Lesson 11-2 Probability
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Example 4: You roll 2 standard number cubes. Determine the odds for each problem
below.
a. Odds(5)
b. Odds(11)
c. Odds(sum is less than 4)
d. Odds(8 or 2)
Homework: p. 697=> 5, 6; pp. 701 – 702 => 4 – 14, 20, 25
Algebra 2: Lesson 11-2 Probability
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