Exclusion Probability (W)
Definition
The proportion of the male reference population that would be excluded as the biological father by the marker panel tested. A high W indicates a discriminating test panel; it does not directly state the probability that the alleged father is the true father.
- Symbol
- W
- Measures
- Proportion of the male reference population excluded by the marker panel
- Interpretation
- High W means a more discriminating panel, not a paternity probability
- Field
- Statistical interpretation of serological relationship evidence
Common questions
Why does a high exclusion probability W not equal a high probability of paternity?+
W describes how well the marker panel discriminates among unrelated men in the reference population. Whether a specific untested man is the true father depends on the likelihood ratio for that individual, which is a separate calculation from the panel's general discriminating power.
How is W used differently from a paternity index in a case report?+
W is typically cited to justify why a panel was chosen or to describe its general power, while a case-specific paternity index or combined paternity index applies the actual test results of the alleged father to state the strength of evidence for that individual.
Related terms
- Combined Paternity Index (CPI)
- The product of all individual paternity indices across all marker systems tested. Assumes independence of the marker systems. The CPI is a...
- Essen-Moller W
- The formula for probability of paternity derived by Erik Essen-Moller in 1938 and widely adopted by forensic laboratories. W = CPI /...
- Obligatory Paternal Allele
- The allele a child must have received from the biological father, identified by subtracting the mother's alleles from the child's genotype. The...
- Paternity Index (PI)
- A likelihood ratio that compares the probability of the observed serological profile if the alleged father is the biological father to the...
- Probability of Paternity (W)
- The posterior probability that the alleged father is the biological father, calculated from the CPI and a prior probability using Bayes' theorem....