Jeffreys scale
Definition
A logarithmic scale for Bayes factors proposed by Harold Jeffreys in Theory of Probability (1961). Levels run from 'barely worth mentioning' at log10(BF) between 0 and 0.5, through 'substantial', 'strong', and 'very strong', to 'decisive' at log10(BF) greater than 2. Widely referenced in forensic science but rarely applied without modification.
Related terms
- ENFSI guideline
- The European Network of Forensic Science Institutes Guideline for Evaluative Reporting in Forensic Science (2015, updated 2016). It defines the propositions framework,...
- Likelihood ratio (LR)
- The ratio of two conditional probabilities: the probability of the observed evidence given the prosecution's hypothesis (same source), divided by the probability...
- Log10(LR)
- The base-10 logarithm of the likelihood ratio, sometimes called the weight of evidence (following I.J. Good). A log10(LR) of 1 corresponds to...
- Transposition fallacy
- The error of treating the probability of the evidence given a hypothesis as though it were the probability of the hypothesis given...
- Verbal equivalence scale
- A table that assigns a verbal phrase to a range of LR values or log10(LR) values. The phrase is used in written...
Explained in
- Strength of Evidence and Likelihood Ratio ScalesA logarithmic scale for Bayes factors proposed by Harold Jeffreys in Theory of Probability (1961). Levels run from 'barely worth mentioning' at log10(BF) betwe...