Probability practice

Total Probability and Bayes' Theorem worksheets

Practice forward total probability and reverse conditional probability with explicit two- and three-source partitions.

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Use the exhaustive, disjoint source branches. Show the total-event sum before any reverse conditional probability, then round only the final result.

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Each worksheet states the sample-space assumptions, distribution support, and counting convention needed for the selected model. Probability tables stay fully labeled, and Bayes questions identify the conditioning event before reversing it.

Learning objective

What this activity builds

Use exhaustive disjoint branches to find a total event probability, then reverse the conditioning correctly with Bayes' theorem.

Worked example

Sources A and B supply 40% and 60% of items; their pass rates are 80% and 90%. Find P(A | pass).

0.40(0.80) / [0.40(0.80)+0.60(0.90)] = 0.372.

The denominator is the total pass probability across both disjoint sources.

Teaching notes

Make the practice count

  • Label priors before conditional rates.
  • Compute the total conditioning-event probability before the Bayes numerator.
  • Check that posterior probabilities stay between 0 and 1.

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Math SheetNameScoreTeacherDateTotal Probability and Bayes' TheoremUse the exhaustive, disjoint source branches. Show the total-event sum before any reverse conditional probability, then round only the final result.1.A randomly selected item passes inspection. Find P(Source B | passes inspection).Assumptions: The source branches are exhaustive and disjoint; the displayed conditional rates apply within their source.SourceP(source)P(passes inspection | source)Source A9/203/10Source B11/2013/202.A randomly selected item comes from the source branches in the table. Find P(passes inspection).Assumptions: The source branches are exhaustive and disjoint; the displayed conditional rates apply within their source.SourceP(source)P(passes inspection | source)Source A3/107/20Source B7/107/10State assumptions and round only the final probability.math-sheet.comPage 1 of 4
Math SheetNameScoreTeacherDateTotal Probability and Bayes' TheoremUse the exhaustive, disjoint source branches. Show the total-event sum before any reverse conditional probability, then round only the final result.3.A randomly selected item comes from the source branches in the table. Find P(passes inspection).Assumptions: The source branches are exhaustive and disjoint; the displayed conditional rates apply within their source.SourceP(source)P(passes inspection | source)Source A1/511/20Source B7/209/10Source C9/202/54.A randomly selected item passes inspection. Find P(Source B | passes inspection).Assumptions: The source branches are exhaustive and disjoint; the displayed conditional rates apply within their source.SourceP(source)P(passes inspection | source)Source A1/101/4Source B7/203/5Source C11/201/10State assumptions and round only the final probability.math-sheet.comPage 2 of 4
Math SheetNameScoreTeacherDateTotal Probability and Bayes' TheoremUse the exhaustive, disjoint source branches. Show the total-event sum before any reverse conditional probability, then round only the final result.5.A randomly selected item passes inspection. Find P(Source B | passes inspection).Assumptions: The source branches are exhaustive and disjoint; the displayed conditional rates apply within their source.SourceP(source)P(passes inspection | source)Source A1/109/10Source B7/202/5Source C11/203/46.A randomly selected item comes from the source branches in the table. Find P(passes inspection).Assumptions: The source branches are exhaustive and disjoint; the displayed conditional rates apply within their source.SourceP(source)P(passes inspection | source)Source A3/1011/20Source B7/109/10State assumptions and round only the final probability.math-sheet.comPage 3 of 4
Math SheetNameScoreTeacherDateTotal Probability and Bayes' TheoremUse the exhaustive, disjoint source branches. Show the total-event sum before any reverse conditional probability, then round only the final result.7.A randomly selected item passes inspection. Find P(Source B | passes inspection).Assumptions: The source branches are exhaustive and disjoint; the displayed conditional rates apply within their source.SourceP(source)P(passes inspection | source)Source A9/203/4Source B11/201/48.A randomly selected item comes from the source branches in the table. Find P(passes inspection).Assumptions: The source branches are exhaustive and disjoint; the displayed conditional rates apply within their source.SourceP(source)P(passes inspection | source)Source A3/1013/20Source B1/43/20Source C9/201/2State assumptions and round only the final probability.math-sheet.comPage 4 of 4

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