title: Statistical sex determination from craniometrics: Comparison of linear discriminant analysis, logistic regression, and support vector machines.
abstract: Accuracy of identification tools in forensic anthropology primarily rely upon the variations inherent in the data upon which they are built. Sex determination methods based on craniometrics are widely used and known to be specific to several factors (e.g. sample distribution, population, age, secular trends, measurement technique, etc.). The goal of this study is to discuss the potential variations linked to the statistical treatment of the data. Traditional craniometrics of four samples extracted from documented osteological collections (from Portugal, France, the U.S.A., and Thailand) were used to test three different classification methods: linear discriminant analysis (LDA), logistic regression (LR), and support vector machines (SVM). The Portuguese sample was set as a training model on which the other samples were applied in order to assess the validity and reliability of the different models. The tests were performed using different parameters: some included the selection of the best predictors; some included a strict decision threshold (sex assessed only if the related posterior probability was high, including the notion of indeterminate result); and some used an unbalanced sex-ratio. Results indicated that LR tends to perform slightly better than the other techniques and offers a better selection of predictors. Also, the use of a decision threshold (i.e. p>0.95) is essential to ensure an acceptable reliability of sex determination methods based on craniometrics. Although the Portuguese, French, and American samples share a similar sexual dimorphism, application of Western models on the Thai sample (that displayed a lower degree of dimorphism) was unsuccessful.
authors.affiliation: University Bordeaux-CNRS-MCC, PACEA, UMR 5199, F-33615 Pessac, France. Electronic address: frederic.santos@u-bordeaux.fr.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Santos
authors.affiliation: University Bordeaux-CNRS-MCC, PACEA, UMR 5199, F-33615 Pessac, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Guyomarc'h
authors.affiliation: University Bordeaux-CNRS-MCC, PACEA, UMR 5199, F-33615 Pessac, France; Charles University, Faculty of Science, Department of Anthropology and Human Genetics, Prague, Czech Republic; West Bohemia University, Faculty of Humanities, Department of Anthropology, Plzen, Czech Republic.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Bruzek
mesh_terms: D002508:Cephalometry; D016002:Discriminant Analysis; D018732:Forensic Anthropology; D006801:Humans; D016015:Logistic Models; D044469:Racial Groups; D015203:Reproducibility of Results; D054881:Sex Determination by Skeleton / Q000379:methods*; D060388:Support Vector Machine
keywords: Accuracy; Forensic anthropology population data; Population; Reliability; Sex estimation; Statistics