Possible or impossible depends on the setup

A bag model containing only two marked colours gives probability words a concrete reference. If the contents change, the judgement may change too; keep the stated situation visible during the discussion.

To hand: A bag model containing only red-marked and blue-marked counters.

List outcomes allowed by the contents. Identify an absent outcome. Explain the judgement using the setup.

What outcomes does this model allow?

Tie probability language to the stated contents and rules. A change to the setup can change what is possible or impossible.

Drawing a green-marked counter is impossible in the stated model when no such counter is present.

Changing the contents changes the judgement. What feature makes the outcome impossible here?

Use visible counters rather than a hidden bag.

List outcomes from the actual contents of the model

Use a picture of a bag containing only red-marked and blue-marked large cards. State the contents clearly and define the task as drawing one card under that fixed setup. A green-marked card cannot be drawn from this model because none is present, not because green is generally an unlikely colour.

Invite learners to name possible outcomes and explain the evidence for each. The list should come from the supplied contents rather than from everything that could conceivably be placed in another bag. Keep the model's boundary visible throughout the discussion.

Change the contents by adding a green-marked card and ask what judgement must change. The earlier statement was accurate under its stated conditions; it is no longer accurate after those conditions are altered. This makes probability language responsive to a setup rather than a collection of permanent labels.

Distinguish impossibility from an outcome not yet observed

Provide a fictional record in which several draws produced red, although blue cards remain in the bag. Blue has not appeared in that small record, but it is still possible under the stated arrangement. Absence from the observations does not establish absence from the permitted outcomes.

Use prepared images or educator handling where suitable. The reasoning does not depend on hiding objects, small loose pieces or dramatic guessing. Learners can point to the contents and dictate an explanation.

For extension, compare two bags with different stated contents and ask whether the same outcome is possible in each. Avoid introducing numerical chances unless the relevant assumptions and number skills are part of the planned task.

Finish with a sentence naming both the outcome and the setup. Green is impossible in this bag is more precise than green is impossible. A useful explanation identifies the feature that supports the judgement and acknowledges what would need to change for the judgement to change. This gives probability vocabulary a concrete evidential foundation instead of treating possible and impossible as words chosen according to a learner's confidence or preference.

Resources

Reflection Journal Template — Use the blank reflection space for observations; write the measurement units and setup separately.

Possible or impossible depends on the setup

What outcomes does this model allow?

List outcomes from the actual contents of the model

Distinguish impossibility from an outcome not yet observed

Resources

Further reading

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