Unit 8, Lesson 3
What Are Probabilities?
Grade 7
Preparation
Lesson Narrative
In this lesson students begin to assign probabilities to events happening from chance experiments. They understand that the greater the probability, the more likely the event will occur. They define an outcome as a possible result for a chance experiment. They learn that the sample space is the set of all possible outcomes, and they understand that a process is called random when the outcome of an experiment is based on chance. If there are equally likely outcomes for a chance experiment, they reason abstractly to find that the probability of each of these outcomes is (MP2).
- Generalize (orally) the relationship between the probability of an event and the number of possible outcomes in the sample space for an experiment in which each outcome in the sample space is equally likely.
- List (in writing) the sample space of a simple chance experiment.
- Use the sample space to determine the probability of an event, and express it as a fraction, decimal, or percentage.
Let’s find out what's possible.
Required Materials
Activity 3
Required Preparation
Print and cut up slips from the blackline master. Each set of slips should be put into a paper bag.
The probability of an event is a number that tells how likely it is to happen. A probability of 1 means the event will always happen. A probability of 0 means the event will never happen.
For example, the probability of selecting a moon block at random from this bag is .
An outcome of a chance experiment is random if it cannot be predicted. For example, the result of rolling a standard number cube is random because it could result in 1, 2, 3, 4, 5, or 6, and nobody can know which value it will be until it is rolled.