Discriminant Function Analysis
Definition
A multivariate statistical technique that derives linear combinations of measurements to maximally separate two or more groups (male and female). The resulting function places an unknown specimen on the discriminant axis and assigns it to the closest group, with an associated posterior probability.
- Method type
- Multivariate statistical classification
- Output
- Group assignment with posterior probability
- Common uses
- Sex estimation from long bones and ancestry estimation from cranial morphology
Common questions
What does discriminant function analysis do in forensic anthropology?+
It classifies unknown skeletal specimens into pre-defined groups (like male/female or ancestral categories) by comparing the specimen's measurements to reference data. The method finds which group the unknown is closest to and assigns it accordingly.
How does the analysis actually assign a specimen to a group?+
It uses linear combinations of measurements to create a discriminant axis, then places the unknown specimen on that axis. The unknown is assigned to whichever group's centroid is closest, and the method outputs a posterior probability showing confidence in that assignment.
What is FORDISC?+
FORDISC is a software package that uses discriminant function analysis as its core analytical engine. It helps anthropologists estimate ancestry from cranial measurements by running the statistical classifications automatically.
Related terms
- Amelogenin
- A gene on both the X and Y chromosomes used for sex determination in forensic STR kits. The X-allele amplicon is approximately...
- Anterior Nasal Spine (ANS)
- A morphoscopic trait: the bony projection at the inferior border of the nasal aperture, scored on a 0-3 scale from absent to...
- Femoral Head Vertical Diameter
- The superoinferior diameter of the femoral head, the most reliable single postcranial sex estimation measurement. US cut-offs (Stewart 1979): below 43.5 mm...
- FORDISC
- Forensic Discriminant Computer program, developed by Ousley and Jantz at the University of Tennessee Knoxville. Performs discriminant-function analysis on user-supplied craniometric measurements...
- Forensic Data Bank (FDB)
- The modern documented skeletal sample within FORDISC, built from cases submitted by US medical examiners since the late 1980s. Provides reference data...
- Geometric Morphometrics
- A method that captures biological shape as a configuration of landmark coordinates, removes position/orientation/scale differences by Procrustes superimposition, and analyses the residual...
- Howells Craniometric Database
- A dataset of 82 standard craniometric measurements on over 2,500 adult skulls from more than 30 population groups worldwide, assembled by W.W....
- Humeral Head Vertical Diameter
- The superoinferior diameter of the humeral head. US cut-offs (France 1998): below 43 mm female, above 47 mm male. Second most commonly...
- Khanpetch 2012
- A South-East Asian long-bone sex estimation study by Khanpetch and colleagues providing population-specific discriminant functions and cut-offs for Thai and South-East Asian...
- Malar Tubercle
- A small bony protuberance on the inferior surface of the malar (zygomatic) bone, scored as present or absent. Higher frequency in East...
- Morphoscopic Traits
- Non-metric cranial features assessed on ordinal or nominal scales (anterior nasal spine, malar tubercle, nasal bone shape, post-bregmatic depression, inferior nasal aperture...
- Population Affinity
- The preferred modern forensic-anthropological term for the relationship between an unidentified individual's skeletal morphology and a modern reference population. Replaces the older...
Explained in these topics
- Ancestry from Cranial Morphology and FORDISCA multivariate statistical method that classifies an unknown specimen into one of several pre-defined groups by finding the group whose covariance-adjusted mul...
- Sex Estimation from Long Bones and the Sub-Adult Sex ProblemA multivariate statistical technique that derives linear combinations of measurements to maximally separate two or more groups (male and female). The resulting...