Prosecutor's fallacy¶
The prosecutor's fallacy confuses the probability of observed evidence given innocence with the probability of innocence given that evidence, typically neglecting base rates and alternative hypotheses.
Core Idea¶
Prosecutor's fallacy is treated here as the recurring crossdomainmodelsstructuresrepresentations identity summarized by this source-grounded definition: The prosecutor's fallacy confuses the probability of observed evidence given innocence with the probability of innocence given that evidence, typically neglecting base rates and alternative hypotheses. The base rate fallacy, also called base rate neglect or base rate bias, is a type of fallacy in which people tend to ignore the base rate (e.g., general prevalence) in favor of the information pertaining only to a specific case.
Scope of Application¶
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Sally Clark case. Sally Clark, a British woman, was accused in 1998 of having killed her first child at 11 weeks of age and then her second child at 8 weeks of age.
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Findings in psychology. This finding has been used to argue that interviews are an unnecessary part of the college admissions process because interviewers are unable to pick successful candidates better than basic statistics.
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False positive paradox. An example of the base rate fallacy is the false positive paradox (also known as accuracy paradox).
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False positive paradox. This paradox describes situations where there are more false positive test results than true positives (this means the classifier has a low precision).
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False positive paradox. The probability of a positive test result is determined not only by the accuracy of the test but also by the characteristics of the sampled population.
Clarity¶
A clear use of Prosecutor's fallacy names the carrier, the operative relation, and the conditions under which the source treats the identity as present. The minimal definition is The prosecutor's fallacy confuses the probability of observed evidence given innocence with the probability of innocence given that evidence, typically neglecting base rates and alternative hypotheses.
Manages Complexity¶
Prosecutor's fallacy compresses multiple crossdomainmodelsstructuresrepresentations details into a stable diagnostic relation. The source shows both the central mechanism—as can be seen from the formula, one needs p(D) for Bayes' theorem, which can be computed from the preceding values using the law of total probability.—and the practical consequence—forensic analysis determines that the perpetrator has a certain blood type shared by 10% of the population.
Abstract Reasoning¶
- Type the carrier. Identify the crossdomainmodelsstructuresrepresentations entities to which the claim applies.
- State the relation. Use the source-grounded identity: The prosecutor's fallacy confuses the probability of observed evidence given innocence with the probability of innocence given that evidence, typically neglecting base rates and alternative hypotheses.
- Check operation and conditions. Further, in the context of detecting terrorism false negatives are highly undesirable and thus must be minimised as much as possible; however, this requires increasing sensitivity at the cost of specificity, increasing false positives. 4.
Knowledge Transfer¶
Within the home domain. Knowledge about Prosecutor's fallacy transfers literally when a new case preserves the same carrier type, relation, and recognition test. Sally Clark, a British woman, was accused in 1998 of having killed her first child at 11 weeks of age and then her second child at 8 weeks of age. This finding has been used to argue that interviews are an unnecessary part of the college admissions process because interviewers are unable to pick successful candidates better than basic statistics. Beyond the home domain. No canonical parent is asserted for Prosecutor's fallacy.
Relationships to Other Abstractions¶
Current abstraction Prosecutor's fallacy Domain-specific
Parents (1) — more general patterns this builds on
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Prosecutor's fallacy is a kind of Informal Fallacy Prime
The prosecutor's fallacy is an informal fallacy that reverses a conditional probability and neglects base rates.
Hierarchy path (1) — routes to 1 parentless root
- Prosecutor's fallacy → Informal Fallacy
Neighborhood in Abstraction Space¶
Prosecutor's fallacy sits in a moderately populated region (44th percentile for distinctiveness): it has near-neighbors but no dense thicket of look-alikes.
Family — Unclustered & Miscellaneous (2551 abstractions)
Nearest neighbors
- Score (statistics) — 0.88
- S-procedure — 0.87
- Youden's J Statistic — 0.87
- Randomized response — 0.87
- Single Vegetative Obstruction Model — 0.87
Computed from structural-signature embeddings · 2026-10-08