Stepwise Discriminant Functions Research Articles

Sex estimation from dimensions of the base of the skull in Black South Africans.

The pelvis and the skull are the two most utilised skeletal elements to estimate sex from skeletonised remains due to their sexually dimorphic traits. However, as increasingly more fragmented remains have been presented for analyses, other bones and their fragments have now been subjected to analyses for sex estimation. In the skull particularly, the base has shown to survive harsh conditions. In this study the foramen magnum region was explored in Black South Africans to estimate sex during forensic analyses. Seven measurements of the foramen magnum and surrounding areas were measured in 120 male and female crania and subjected to discriminant function analyses. The average accuracies for the stepwise discriminant functions ranged from 60-71% whilst the average accuracies for the direct discriminant functions ranged from 63-69%. The average accuracies obtained in this study are similar to other studies performed using the foramen magnum. However, these average accuracies are much lower than other skeletal elements that have been used for sex estimation in South Africans. Thus, the equations in this study should be used with caution and only in the absence of more accurate elements. The cranial base has always shown to have a low to moderate expression of sexual dimorphism. The cranial base of Black South Africans is no different.

Estimating sex among South African groups using the dentition

Biological profiles are used to assist in the identification of an unknown person. Sex estimation is important in this process as other aspects of the biological profile such as age-at-death, population affinity and stature depend on accurate sex estimates. While the pelvis and long bones, respectively, take preference over the dentition and cranium for sex estimation, dentition remains a good proxy for this parameter due to their post-mortem longevity. The purpose of this study is to examine dental size variation in incisors, canines, premolars and molars of black, white and coloured South Africans and to use discriminant function statistics (LDA) to develop population-specific formulae for the estimation of sex. A total of 906 adult crania were analysed. Measurements included four permanent tooth crown dimensions: maximum mesiodistal, maximum buccolingual and molar diagonal diameters (mesio-buccal – disto-lingual and mesio-lingual – disto-buccal). Statistical analyses included TEM, Student’s t-test, ANOVA, and discriminant function analysis (DFA). Dental dimensions are repeatable with low intra and inter-observer errors ranging from 0.09% to 4.17% and 0.18–6.17%, respectively. Of the 36 dental variables, 26 were statistically significant for biological sex and 17 for population affinity, and included all tooth types. Stepwise discriminant functions with a LOOCV provided correct classification rates of up to 86% for sex. The raw data for the dentition of black, white and coloured South Africans is provided on https://doi.org/10.5281/zenodo.5226935.

Anelaphus villosus (Fabricius) and A. parallelus (Newman) (Coleoptera: Cerambycidae) can be accurately distinguished using body measurements and DNA barcoding

AbstractAnelaphus villosus (Fabricius) and A. parallelus (Newman) are longhorned beetles (Coleoptera: Cerambycidae: Cerambycinae: Elaphidiini) that closely resemble each other in appearance. In practice, if antennomere 3 is distinctly longer than antennomere 4, the specimen is considered to be A. villosus, but the accuracy of this methodology is unknown. Authorities disagree about the ease of separating these two species based on morphological traits, and recent work hypothesises that they should be synonymised due to the difficulty of distinguishing them by either morphology or natural history. Assuming correct initial species determinations of curated specimens, as well as of those determined with DNA barcoding and by the primary author, data from 23 body measurements were collected from 50 A. villosus and 60 A. parallelus specimens. Stepwise discriminant analyses and discriminant functions were used to evaluate the ability to distinguish these species based on morphology. Species assignments from discriminant functions were very accurate and were supported by assignments determined with DNA barcoding. The ability to distinguish A. villosus and A. parallelus based on morphological and molecular differences provides evidence against the taxonomic hypothesis of synonymy under one species. A need for greater ecological understanding of these species remains.

Gender determination by odontometric method.

Context:Gender determination is central in establishing personal identification from human skeletal remains. The study was conducted to find out the accuracy with which gender can be determined by odontometric methods.Aims:To investigate the mesiodistal (MD) and buccolingual (BL) dimensions of all the teeth of permanent dentition to find new parameters to differentiate between male and female teeth and to assess whether each type of linear measurement can be used independently in odontometric sex differentiation.Materials and Methods:The study was conducted at a dental college on a composite group of 500 individuals comprising 250 males and 250 females. Impressions of upper and lower jaws were made with alginate impression material and casts prepared with dental stone. A digital Vernier calliper was used to measure the BL and MD dimensions of all the upper teeth except the third molars.Statistical Analysis Used:The results were subjected to statistical analysis using univariate analysis and linear stepwise discriminant function analysis to find the variables which discriminate gender significantly.Results:The MD and BL dimensions between males and females were statistically significant. The predicted value for correct classification of gender was also statistically significant.Conclusions:The ability to differentiate gender in the population using stepwise discriminant functions was found to be very high with 99.8% accuracy with males showing statistically larger teeth than females. This is similar to the near 100% success in gender determination using pelvic and skull bones.

Sex estimation using diagonal diameter measurements of molar teeth in African American populations

Teeth are often recovered in forensic cases due to their postmortem longevity. The goal of the present research was to investigate the degree of sexual dimorphism in the permanent molars of African Americans using crown and cervical diagonal diameters. Discriminant functions developed from a modern Greek population were tested for accuracy of sex estimation in an African American population. One hundred and three (53 males and 50 females) individuals ranging in age from 16 years to 66 years old were used from the Robert J. Terry Anatomical Skeletal Collection. Four diagonal diameter measurements were taken for each of the left mandibular and maxillary molars: mesiobuccal-distolingual crown diameter, mesiolingual-distobuccal crown diameter, mesiobuccal-distolingual cervical diameter, and mesiolingual-distobuccal cervical diameter. The overall percentage of accuracy of the modern Greek discriminant functions when applied to the African American sample was between 53.8% and 63.6%. Males were more accurately classified (93.6%–100%) than females (0%–18.2%). The African American population specific direct discriminant functions showed accuracy rates from 72.6% to 100% for the original data and 40%–72.3% for the cross-validated data. The African American stepwise discriminant functions showed accuracy rates from 63.9% to 77.6% for the original and cross-validated data. Comparisons to other populations were made. The results suggest that, in teeth, there is variation in the degree of sexual dimorphism between populations and discriminant functions for sex estimation in dentition are population specific.

Odontometric sex variation in Malaysians with application to sex prediction

Information about the sex of individuals is important for human identification. This study was conducted to quantify classification rates of sex prediction models for Malaysians using odontometric profiles. Mesiodistal (MD) and buccolingual (BL) crown dimensions of the permanent dentition were studied in 400 young adult Malaysians, giving a total of 28 tooth size variables. The sample consisted of three major ethnic groups, the Malays, Chinese and Tamils, since the aim was to assess sex dimorphism in Malaysians as a whole. Results showed that the mesiodistal diameter of the lower canine was the most sexually dimorphic dimension in Malaysian Malays and Tamils. Univariate analyses showed that the magnitude and pattern of sex dimorphism varies between these three ethnic groups, with Malaysian Chinese and Tamils being more dimorphic than the Malaysian Malays. Stepwise discriminant functions were generated bearing in mind their application in practical forensic situations. The range of classification rates was from 70.2% to 78.5% for the composite Malaysian group, and 83.8%, 77.9%, 72.4% for Malaysian Chinese, Malays and Tamils, respectively. The ‘Area Under the Receiver Operating Characteristic Curve statistics’ indicated good classification rates for three prediction models obtained using a combination of all tooth size variables, mandibular teeth, and mesiodistal dimensions in the composite Malaysian group, and for all tooth size variables in each ethnic group. The present study provides strong support for the value of odontometry as an adjunct scientific method for sex prediction in human identification.

Geometric Morphological Differences Distinguish Populations of Scup in the Northwestern Atlantic Ocean

AbstractScup Stenotomus chrysops, a commercially important marine species, are distributed from Nova Scotia to south Florida, and may represent morphologically distinct populations across their range. It was determined whether there were morphological differences between a North Atlantic Bight (NAB) population (41°N) and two South Atlantic Bight (SAB) populations (30°N and 32°N) of this species from April 2005 to July 2005, when the populations had formed spawning groups. Morphology was compared among populations by means of a geometric, landmark‐based analysis of morphological and meristic traits for 180 individuals that were sexed and staged to maturity. A backward, stepwise discriminant functions analysis (DFA) produced a model that generated DFA scores that differed significantly between the NAB and SAB populations. Forehead and body depth dimensions differed among populations but not sexes. The DFA model predicted similar scores for 32 new NAB individuals and 31 new SAB individuals; however, scores were consistently underpredicted for the NAB individuals and overpredicted for the SAB individuals. We concluded that distinct northern and southern populations support a two‐stock or two‐species hypothesis; however, it is unclear whether this stock structure is related to reproductive or other life history traits. Either phenotypic plasticity or divergent selection may explain the morphological dissimilarities among these populations, but their influence on individual fitness remains unknown.

Preliminary Validation of the MMPI--A for a Male Delinquent Sample: An Investigation of Clinical Correlates and Discriminant Validity

Adolescent psychopathology, until recently, has been a largely neglected area of research and poses unique challenges for psychological assessments. In response to the specific need for adolescent-focused measures, the MMPI-A (Butcher et al., 1992) was among several measures to be developed. Although a sizeable literature exists on the original MMPI (Hathaway & McKinley, 1943) and adolescent populations, relatively few empirical studies have been published on the MMPI-A. The primary purpose of this study was the examination of clinical correlates for the MMPI-A for a male delinquent sample. MMPI-A protocols were collected from 99 adolescents at a North Texas juvenile correctional facility, and systematic comparisons were conducted between the Basic Scales and symptoms/diagnoses derived from the Schedule of Affective Disorders and Schizophrenia for School-Age. Children (K-SADS-III-R; Ambrosini, Metz, Prabucki, & Lee, 1989). Using only K-SADS-III-R symptoms with high reliabilities (rs > .80), a comprehensive list of correlates was generated for the Clinical, Supplementary, and Content Scales. Additionally, stepwise discriminant functions successfully classified MMPI-A protocols according to K-SADS-III-R diagnoses. As an exploratory analysis, ethnic differences on MMPI-A profiles were also investigated, revealing significant differences among groups.

The differential effects of simulating malingering, closed head injury, and other CNS pathology on the Wisconsin card sorting test: Support for the “Pattern of performance” hypothesis

We investigated the effects of faking bad on the Wisconsin Card Sorting Test, comparing the performance of simulating malingerers ( M; n = 24) to controls ( C; n = 21), closed head-injured patients ( CHI, n = 70), and patients with mixed CNS pathology other than CHI alone ( CNS; n = 89). Stepwise discriminant functions achieved good accuracy (91–96%), sensitivity (58–100%), and specificity (92–100%) in differentiating simulating malingerers from these groups. The Categories score was a consistent significant independent discriminating variable. Categories alone could differentiate between the M and C groups. However, in discriminating between simulating malingerers and both CHI or CNS patients, more complex patterns of performance emerged, consisting of relatively poorer performance ratios on Categories compared to Perseverative Errors. This supported the Pattern of Performance theory of the effects of simulating malingering on neuropsychological tests, which holds that people simulating malingering do more poorly on obvious vs. subtle tasks compared to people with verified brain damage. Due to the difficulty of tracking one's performance on several different indices simultaneously, known patterns of performance for patients with verified brain dysfunction should be very difficult to fake, even with coaching.

The differential effects of simulating malingering, closed head injury, and other CNS pathology on the Wisconsin card sorting test: Support for the "Pattern of performance" hypothesis

We investigated the effects of faking bad on the Wisconsin Card Sorting Test, comparing the performance of simulating malingerers ( M ; n = 24) to controls ( C ; n = 21), closed head-injured patients ( CHI , n = 70), and patients with mixed CNS pathology other than CHI alone ( CNS ; n = 89). Stepwise discriminant functions achieved good accuracy (91–96%), sensitivity (58–100%), and specificity (92–100%) in differentiating simulating malingerers from these groups. The Categories score was a consistent significant independent discriminating variable. Categories alone could differentiate between the M and C groups. However, in discriminating between simulating malingerers and both CHI or CNS patients, more complex patterns of performance emerged, consisting of relatively poorer performance ratios on Categories compared to Perseverative Errors. This supported the Pattern of Performance theory of the effects of simulating malingering on neuropsychological tests, which holds that people simulating malingering do more poorly on obvious vs. subtle tasks compared to people with verified brain damage. Due to the difficulty of tracking one's performance on several different indices simultaneously, known patterns of performance for patients with verified brain dysfunction should be very difficult to fake, even with coaching.

Correlative study of human papillomavirus DNA, histopathology and morphometry in cervical condyloma and intraepithelial neoplasia.

This study includes 28 intraepithelial squamous lesions of the cervix associated with human papillomavirus (HPV) DNA sequences detected by the Southern blot technique. Objective analyses of the histologic features by morphometric parameters and mitotic index have demonstrated that lesions of HPV types 6 and 11 can be distinguished from types 16, 18, and 33 by stepwise discriminant functions. The latter lesions have higher mitotic and cellularity indexes and greater nuclear atypia than the former, supporting a greater degree of epithelial proliferation and abnormality seen in association with HPV types 16/18/33.

Subject characteristics as predictors of self-change in smoking

Subject characteristics served as predictors of smokers' success or failure in their self-change efforts at smoking cessation over a 6-month period. Seven hundred and three adult subjects represented five stages of change based on the transtheoretical model: precontemplation, contemplation, action, maintenance, and relapse. Step-wise multiple discriminant functions were used to predict movement across the stages. Health problems, problem duration, daily cigarettes, previous attempts to quit, and smoking for pleasure predicted movement through various stages of change. The stronger the smoking habit, the less apt the smoker is to quit or maintain a nonsmoking status. Smokers with higher incomes and more years of education are more likely than persons of lower socioeconomic levels to be successful in their self- change efforts. The advantages of process-oriented rather than static variables for predicting self-change are discussed.

Distinguishing among Three Subgroups of Handicapped Students Using Bannatyne’s Recategorization

AbstractThis study examines the utility of the Ban- natyne recategorization system in discriminating among three groups of handicapped students. A stepwise discriminant functions analysis was performed on the subtest scaled scores from the WISC-R for 294 learning disabled (LD), 36 educably mentally retarded (EMR), and 71 emotionally disturbed (ED) students. The results of this analysis revealed that 100 percent of the EMR and ED students were predicted to be labeled LD on the basis of this recategorization, while 99.7 percent of the LD students were predicted to be LD. These findings are examined in relation to the use of alternative statistical methods and different diagnostic procedures to identify and classify students.

Comparison of Multivariate Techniques in the Prediction of Juvenile Postparole Outcome

Several strategies for the prediction of institutional outcome have been attempted by researchers in juvenile and parole prediction. The majority of researchers have utilized a variation of multiple regression, while a few have made use of discriminant functions and factor analysis. The present study contrasted the three approaches in terms of predictive efficiency for juvenile recidivism. A total of 579 juvenile cases were selected from the Washington state juvenile archives during the calendar year of 1971. Forty predictive variables from personal histories and behavioral records of the Office of Juvenile Rehabilitation were collated and quantified for the study. The total sample was divided randomly into two groups for purposes of double cross-validation. On each of the two sample halves, a set of predictors of juvenile outcome were generated by each of three methods, factor analysis, stepwise regression, and stepwise discriminant functions. Validation of the three methods was assessed by (1) D2 or discriminability of each predictive variable on the cross-validation sample, and (2) the accuracy of classifying each juvenile based on discriminant analyses. The results showed clearly that stepwise discriminant functions provided the more consistent selection of variables with seven of 10 variables the same for all samples. Also, discriminant functions was shown to manifest the most predictive efficiency with significantly fewer misclassifications and greater discriminability. By contrast, stepwise regression and factor analysis as strategies manifested more misclassifications and less discriminability. In addition, the two methods were found to be unreliable in the selection of predictive variables for the two validation samples. Results were discussed in terms of the shrinkage problems of regression analyses and the homogeneity of variance associated with factor analysis.

On stepwise discriminant analyses applied to physiologic data.

ABSTRACTRecently widespread interest has arisen in the use of stepwise discriminant function techniques with evoked physiologic data. The purpose of this presentation is to discuss in non‐mathematical terms how such analyses can easily be misused and misinterpreted, pointing out specific pitfalls to be avoided. The various statistical tests of hypotheses used with stepwise discriminant functions, predominantly in the BMDO7M computer program, are discussed in relationship to the law of the iterated logarithm. This law clearly shows how highly significant differences will almost always be found when a stepwise procedure is used even though there may be no real differences between groups. As an empirical illustration, a series of physiologic data (EKG and EEG) was collected under stimulus and no stimulus conditions. Stepwise analyses consistently produced significant differences under no stimulus conditions whereas nonstepwise procedures did not. Under stimulus conditions, stepwise analyses consistently exaggerated the extent of differences detected by nonstepwise analyses.