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Life · Guided lesson

Compare theoretical chance with repeated trials

About 13 minutes · 3 reading + 10 practice and checks
Time includes reading, practice, and questions. Extra videos or further study are optional.
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A chance-model packet with a complete sample space, combined-event calculations, conditional probabilities and a repeated-trial comparison.

Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.

What to include

  • List a complete equal-outcome sample space.
  • Calculate a complement and an independent combined event.
  • Audit overlap in an inclusive-or event.
  • Compare conditional and unrestricted denominators.
  • Explain observed frequency versus theoretical chance with all six changed cases.

Review and revise

Use these criteria to check your work and choose what to improve.

  • Method: applies the course-specific rules to the supplied cases with visible intermediate work.
  • Accuracy: results agree with the stated facts, units, boundaries and independent checks.
  • Reasoning: explains why the result follows and identifies a limitation or unresolved question.
  • Transfer: completes changed cases and revises the final project when a relevant assumption changes.
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Before you begin

The idea in everyday life

Case: a modeled fair coin predicts heads probability 0.5. Supplied simulated record:20 tosses,12 heads and 8 tails. These are fictional teaching results.

The idea

A theoretical model describes chance under assumptions; observed relative frequency describes a particular record. Random variation means a short record need not equal the model exactly. More trials do not guarantee exact equality or prove fairness by themselves.

Follow along

Compare theoretical chance with repeated trials — worked practice

A theoretical model describes chance under assumptions; observed relative frequency describes a particular record. Random variation means a short record need not equal the model exactly. More trials do not guarantee exact equality or prove fairness by themselves.

Case: a modeled fair coin predicts heads probability 0.5. Supplied simulated record:20 tosses,12 heads and 8 tails. These are fictional teaching results.

Original practice material

Paste at A1.

AMaterialBSupplied text
CaseCase: a modeled fair coin predicts heads probability 0.5. Supplied simulated record:20 tosses,12 heads and 8 tails. These are fictional teaching results.

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  1. 1. 1. Model

    State the theoretical chance and expected count.

    You should see: 0.5; expected heads 20×0.5=10.

  2. 2. 2. Observe

    Calculate the record’s relative frequency.

    You should see: 12/20=0.6.

  3. 3. 3. Compare

    Record the count difference and probability difference.

    You should see: Two extra heads; relative frequency differs by 0.1.

  4. 4. 4. Bound

    Explain what this small record establishes.

    You should see: The record differs from the fair model; it alone does not prove the coin is unfair.

Now change one thing

A fictional 100-trial record has 54 heads. Enter the relative heads frequency.

Your work

What to finish

A model-versus-record comparison with expected counts and limitations.

Common mistake

Watch for this

Probability one-half describes the model, not a fixed quota in every short sequence; retain the observed discrepancy and the model assumption.

How can I tell I understand it?

Explain a changed trial record without promising exact balance or inferring fairness from one tally.

Try 3 questions

Quick knowledge check

Answer all 3 questions. Get at least 2 right and the lesson completes automatically.

Not yet passed

You’ll get an explanation for each answer. Signed in? Your results save to your account.

1A modeled 0.25 event is tested 80 times. What is its expected count?
2A 20-trial record has 7 successes. What is relative frequency?
3Why can twelve heads in twenty tosses occur under a fair-coin model?
0 of 3 answeredApply the lesson to a short question, then review the explanation.
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Finish this lesson

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Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.

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Sources and further reading

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OpenStax: probability terminology
Source & access notes · checked 2026-10-01

Web open/search showed the official page, its topic heading and relevant concept description. This is a content/source check, not a provider endorsement.

Access: Official page retrieved with the web reader on 2026-10-01; interactive tools and videos were not certified by retrieval.

Reuse: Original fictional teaching cases, calculations, questions and examples; link and short factual paraphrase only. No copied source exercises or illustrations.

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