Discriminant Function Analysis (DFA)
Definition
A multivariate statistical method that builds a weighted linear equation from measurements to classify specimens into groups (here, male or female). A DFA trained on a known-sex reference sample gives maximum discriminating power and can be applied to an unknown; accuracy depends on how well the reference population matches the target.
- Method type
- Multivariate statistical classification
- Output
- Weighted linear equation for group assignment
- Typical use
- Sex estimation from skeletal or dental measurements
- Field
- Forensic anthropology and odontology
Common questions
Why does DFA accuracy depend on the reference population used to train it?+
The equation's weights are derived from measurements of a known-sex sample, so if that sample's body proportions or dental dimensions differ systematically from the unknown individual's population (due to ancestry, secular change, or geography), classification accuracy on the unknown drops.
Can DFA give a definite sex determination on its own?+
It produces a probability-based classification with a stated accuracy rate for the reference sample used, so results are reported with that uncertainty rather than as a certain determination, particularly for measurements falling near the classification boundary.
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...
- Barr Body
- A condensed, transcriptionally inactive X chromosome visible in the interphase nuclei of XX individuals. In dental cells it appears as a small...
- Mandibular Canine Index (MCI)
- The ratio of mandibular canine mesiodistal crown width to intercanine distance, multiplied by 100. Values above a population-specific threshold lean male. Described...
- Odontometrics
- The quantitative measurement of teeth, covering crown diameters, root lengths, and cusp dimensions. In forensic practice these measurements feed discriminant function analyses...
- Sexual Dimorphism
- Systematic physical differences between biological males and females of a species. In teeth it is expressed mainly as size: males average larger...