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Grade 10 · lesson 2 of 4

Compare Recall with the Correct Denominator

Divide detected positives by the number of actual positives in the supplied labeled set.

About 22 minutes, plus any extended practice

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Supplied materials

  • Paper and pencil; answers may also be spoken or typed.
  • All cases, labels, numbers and rules are supplied on this page. No real account, private information or purchase is needed.

Learn the idea

Recall for a positive category is true positives divided by all actual positive labeled cases. It differs from precision, which uses predicted positives. A group comparison should preserve denominators and sample sizes. The supplied cases calculate recall only and do not establish fairness for every possible criterion.

Divide detected positives by the number of actual positives in the supplied labeled set. Do not use all predictions or predicted positives as the recall denominator.

Use this supplied case: Labeled set: 4 actual positives; model detects 3 of them. Positive-category recall percentage? The task is to connect the given information to the computing idea. Write a short evidence trail so another learner can reproduce your choice. The simplified case describes the stated model, not every real system.

  1. Represent the supplied worked case with a labeled drawing, table or short trace.
  2. Divide detected positives by the number of actual positives in the supplied labeled set.
  3. Explain why the worked answer fits and why one alternative does not.
  4. Try the new check and practice cases; revisit the stated rule if your evidence does not match.
Worked example

See the method in action

The labeled set has 4 actual positives, and the model detects 3. Recall=3/4=0.75=75%. The undetected positive stays in the denominator because the question is how many actual positives were found. The predicted-positive count is a different denominator used for precision. This recall result describes the supplied cases only; it does not establish fairness, safety, or successful performance in a real deployment.

Your turn

Check your reasoning

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Helpful tips
  • Divide detected positives by the number of actual positives in the supplied labeled set.
  • Do not use all predictions or predicted positives as the recall denominator.
Labeled set: 5 actual positives; model detects 4 of them. Positive-category recall percentage?

Feedback appears here after you check. This is practice, not a graded school assessment.

See the answer and explanation

80%

Using the supplied inputs: ((100*4)/5) = 80.0. Divide detected positives by the number of actual positives in the supplied labeled set. Do not use all predictions or predicted positives as the recall denominator.

Take it further

Actual positives 20, detected 15 give 75%recall. Predicted positive count is not the recall denominator.

Nothing here is saved to an account or sent to a teacher. The answer download includes your current choice and any checked feedback. It does not include choices from the separate More practice section. Download that section separately.

More practice: try new cases

Choose an answer for each problem. Explain your method on paper, then use the feedback to decide what to revisit.

More practice: try new cases
1. Labeled set: 8 actual positives; model detects 6 of them. Positive-category recall percentage?
Need a hint?
  • Divide detected positives by the number of actual positives in the supplied labeled set.
  • Do not use all predictions or predicted positives as the recall denominator.
2. Labeled set: 10 actual positives; model detects 7 of them. Positive-category recall percentage?
Need a hint?
  • Divide detected positives by the number of actual positives in the supplied labeled set.
  • Do not use all predictions or predicted positives as the recall denominator.
3. Labeled set: 10 actual positives; model detects 8 of them. Positive-category recall percentage?
Need a hint?
  • Divide detected positives by the number of actual positives in the supplied labeled set.
  • Do not use all predictions or predicted positives as the recall denominator.

Your choices are temporary. Feedback appears after you check all the answers.

Nothing here is saved to an account or sent to a teacher. Keep your own notes or download them before leaving. The score describes these questions; it does not certify subject mastery.

Check the subject sources

These LifeStarter passages, scenarios and exercises are authored for this Academy with AI assistance and review. External resources keep their publishers’ terms. A grade label suggests a starting level; it does not establish alignment with your school’s complete requirements.