More Estimating Probabilities

5 min

Teacher Prep
Setup
2 minutes of quiet work time followed by whole-class discussion.

Narrative

The purpose of this Warm-up is for students to think more deeply about probabilities and what the values actually represent. In this activity, students are asked to compare the likelihood of three events with probabilities given in different formats. In the discussion, students are also asked to think about the context of the situations to see that probabilities are not the only consideration when planning a response.

Launch

Give students 2 minutes of quiet work time followed by a whole-class discussion. 

Student Task

  1. If the weather forecast calls for a 20% chance of light rain tomorrow, would you say that it is likely to rain tomorrow?
  2. If the probability of a tornado today is 110\frac{1}{10}, would you say that there will likely be a tornado today?
  3. If the probability of snow this week is 0.85, would you say that it is likely to snow this week?

Sample Response

  1. It is not likely to rain tomorrow, but it could happen.
  2. The tornado is not likely to happen today, but it could happen.
  3. It is likely that it will snow this week, but it might not happen.
Activity Synthesis (Teacher Notes)

Ask students, “Which situation would you worry about the most? Is that the same situation that is the most likely?”

Note that our interpretation of the scenarios influences how we feel about how likely an event is to happen. Although the likelihood of rain is higher, the implications of a tornado are much greater, so we may be more likely to worry about the tornado than the rain.

Standards
Addressing
  • 7.SP.5·Understand that the probability of a chance event is a number between 0 and 1 that expresses the likelihood of the event occurring. Larger numbers indicate greater likelihood. A probability near 0 indicates an unlikely event, a probability around 1/2 indicates an event that is neither unlikely nor likely, and a probability near 1 indicates a likely event.
  • 7.SP.C.5·Understand that the probability of a chance event is a number between 0 and 1 that expresses the likelihood of the event occurring. Larger numbers indicate greater likelihood. A probability near 0 indicates an unlikely event, a probability around 1/2 indicates an event that is neither unlikely nor likely, and a probability near 1 indicates a likely event.

20 min

10 min