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Mubarak A Bidmos - One of the best experts on this subject based on the ideXlab platform.
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Accuracies of Discriminant Function equations for sex estimation using long bones of upper extremities
International Journal of Legal Medicine, 2020Co-Authors: Mubarak A Bidmos, Pedzisai MazengenyaAbstract:One of the scopes of practice of forensic anthropologists is the estimation of sex from skeletal remains. As a result, population-specific Discriminant Function equations have been developed from measurements of various bones of the human skeletons. Steyn, Patriquin ( Forensic Sci Int 191 (1-3):113, 2009 ) noted that the lack of skeletal collections and data from most parts of the world has made this process impractical. Previous attempts to develop global Discriminant Function equations from measurements of the pelvis showed that population-specific equations are not necessary as equations derived from other populations yielded high sex estimation scores when applied to a different population. However, information on the suitability and applicability of generalised equations in sex estimation using long bones is still scarce. It is, therefore, the aim of this study to assess the accuracies of population-specific Discriminant Function equations derived from measurements of long bones of the upper limb of South African population groups. Data analysed in the current study were obtained from Mokoena, Billings, Bidmos, Mazengenya ( Forensic Sci Int 278:404, 2017 ) and Mokoena, Billings, Gibbon, Bidmos, Mazengenya ( Science & Justice 6(59):660–666, 2019 ) in which a total sample of 988 bones (humeri, radii, and ulnae) of South Africans of African descent (SAAD), South Africans of European descent (SAED) and Mixed Ancestry South Africans (MASA) were measured. Stepwise and direct Discriminant Function analyses were performed on the pooled data. Each Function was used to estimate the sex of cases in each population group separately and average accuracies calculated. Thereafter, population-specific Discriminant Function equations were formulated for each population group and then applied to other population groups. The average accuracies of Functions for pooled data ranged between 80.7 and 86.5%. The cross-validation average accuracies remained unchanged for most Functions, confirming the validity of derived Functions. A drop in average accuracies (0.8–5.3%) was observed when the Functions were tested on a sample of SAAD while increased average accuracy was observed for the SAED and MASA (0.5–6.9%). When population-specific Functions for a particular population group were applied to other groups, a wide range of a drop in average accuracies was observed (1.3 to 22.4%). This thereby confirms that population-specific equations should not be applied to other population groups. However, Discriminant Function equations from the pooled data of South Africans are accurate in the estimation of sex and efforts should be made towards the development and validation of such equations from as many bones of the human skeleton.
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the skull and humerus in the determination of sex reliability of Discriminant Function equations
Forensic Science International, 2009Co-Authors: Meredith Stacy Robinson, Mubarak A BidmosAbstract:Abstract Sex determination plays a crucial role in the identification of human remains as it narrows the possibility for identification by 50%. The purpose of this study is to test the validity of five Discriminant Function equations, with accuracies of 80% and higher, that have been derived by Steyn and Iscan [M. Steyn, M.Y. Iscan, Sexual dimorphism in the crania and mandibles of South African Whites, Forensic Sci. Int. 98 (1998) 9–16; M. Steyn, M.Y. Iscan, Osteometric variation in the humerus: sexual dimorphism in South Africans, Forensic Sci. Int. 106 (1999) 77–85] for the skull and humerus of South Africans of European Descent (SAED). These equations were tested on different regional populations of SAED within South Africa. While the validity of some of the Discriminant Functions has been assessed by the authors who derived them, no other previous independent study has been carried out to assess the reliability of these equations. In addition, these equations have not been tested on skeletons located outside the Gauteng province. The study sample consisted of 230 skulls and 264 humeri of SAED obtained from four South African skeletal collections: Raymond A. Dart Collection of Human Skeletons (Johannesburg); Pretoria Bone Collection; Cape Town Skeletal Collection; and the Osteology Archive Student Collection (Stellenbosch). A total of 14 measurements (12 cranial and 2 humeral) were taken on these skeletal elements. The observed accuracies from the present study (72.0–95.5%), with the exception of one sample's accuracy, compared well with the original classification rates (80.2–92.5%) for most of the Functions thereby confirming the validity of the Discriminant Function equations for sex determination for the skull and humerus of SAED, for SAED in all regions of South Africa.
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an assessment of sex using the skull of black south africans by Discriminant Function analysis
Homo-journal of Comparative Human Biology, 2008Co-Authors: Manisha R Dayal, Muhammad A Spocter, Mubarak A BidmosAbstract:The derivation of Discriminant Function equations for skeletal elements of South African populations continues to be an area of interest to both forensic anthropologists and skeletal biologists alike. The skull of black South Africans has previously been subjected to Discriminant Function analysis, using four measurements and two indices; however, no equations were derived to address the issue of sex determination. Recently Franklin, Freedman and Milne [2005. Sexual dimorphism and Discriminant Function sexing in indigenous South African crania. HOMO J. Comp. Hum. Biol. 55, 213-228] used the crania of black South Africans, in a three-dimensional approach, with eight linear measurements to investigate sex determination. This study, although valuable, requires the use of highly technical and expensive morphometric equipment that renders it less feasible in South Africa. In response to this, our study uses traditional anthropometric measurements and equipment to address the question of sex determination from the crania and mandible of blacks. One hundred and twenty non-pathological skulls were randomly selected from the Raymond Dart Collection of Human Skeletons, equally distributed by sex and belonging to individuals whose age at death ranges between 25 and 70 years. Fourteen cranial and six mandibular measurements were subjected to Discriminant Function analyses and Discriminant Function equations were derived for sex determination. Average accuracies ranged between 80% and 85% and were on par with that obtained in previous studies. Our study shows that traditional methods provide average accuracies that are comparable to those obtained using more complex techniques.
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further evidence to show population specificity of Discriminant Function equations for sex determination using the talus of south african blacks
Journal of Forensic Sciences, 2004Co-Authors: Mubarak A Bidmos, Manisha R DayalAbstract:Several studies have shown that osteometric differences exist between different population groups. Thus, Discriminant Function equations derived for the determination of sex from skeletal elements are population specific. In a previous study, the authors derived such equations from nine measurements of the talus of South African whites with high levels of average accuracies. The validity of some of the equations was tested on data collected from a South African black sample that consisted of 120 tali, equally distributed by sex, derived from the Raymond A. Dart Collection of Human Skeletons. The average accuracies dropped significantly. This necessitated the derivation of new equations for the South African black population and the average accuracies obtained ranged between 80% and 89%. The validity of the equations derived from the present study was tested using the leave-one-out classification and two independent samples (1 and 2). The applicability of the equations with very high classification rate from the present study was tested on Independent sample 1 of 10 white tali with poor results. The result of the validity of these equations on an Independent sample 2 of 10 black tali revealed acceptably high average accuracies in correct classification thereby supporting earlier observations on population specificity of Discriminant Function equations.
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Discriminant Function sexing of fragmentary femur of south african blacks
Forensic Science International, 2004Co-Authors: Samuel A Asala, Mubarak A Bidmos, Manisha R DayalAbstract:When fragmentary and incomplete bones are all that are available to the forensic anthropologist for use in sex determination, non-metric and metric sex discriminating parameters that have been derived from complete bones may be of little use. In such circumstances, sex discriminating metric methods that are of specific application to fragmentary bones will be more useful. Since such studies have not been systematically carried out in bones of South African blacks, the aim of this study was to begin to provide such data. Two hundred and twenty left femurs of black South Africans were obtained from the Raymond A. Dart Collection of African Skeleton, School of Anatomical Sciences, University of the Witwatersrand, South Africa. Five variables from the upper end of the femur and three variables from the lower end of the femur were measured and subjected to univariate and multivariate Discriminant Function analyses. The vertical head diameter and the medial condylar length were most successful in sex identification from the upper and lower ends of the femur respectively. The combined variables were more useful than the use of variables individually. Discriminant Function score equations were derived for individual and combined variables from the upper and lower ends of the femur of the South African blacks.
Manisha R Dayal - One of the best experts on this subject based on the ideXlab platform.
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an assessment of sex using the skull of black south africans by Discriminant Function analysis
Homo-journal of Comparative Human Biology, 2008Co-Authors: Manisha R Dayal, Muhammad A Spocter, Mubarak A BidmosAbstract:The derivation of Discriminant Function equations for skeletal elements of South African populations continues to be an area of interest to both forensic anthropologists and skeletal biologists alike. The skull of black South Africans has previously been subjected to Discriminant Function analysis, using four measurements and two indices; however, no equations were derived to address the issue of sex determination. Recently Franklin, Freedman and Milne [2005. Sexual dimorphism and Discriminant Function sexing in indigenous South African crania. HOMO J. Comp. Hum. Biol. 55, 213-228] used the crania of black South Africans, in a three-dimensional approach, with eight linear measurements to investigate sex determination. This study, although valuable, requires the use of highly technical and expensive morphometric equipment that renders it less feasible in South Africa. In response to this, our study uses traditional anthropometric measurements and equipment to address the question of sex determination from the crania and mandible of blacks. One hundred and twenty non-pathological skulls were randomly selected from the Raymond Dart Collection of Human Skeletons, equally distributed by sex and belonging to individuals whose age at death ranges between 25 and 70 years. Fourteen cranial and six mandibular measurements were subjected to Discriminant Function analyses and Discriminant Function equations were derived for sex determination. Average accuracies ranged between 80% and 85% and were on par with that obtained in previous studies. Our study shows that traditional methods provide average accuracies that are comparable to those obtained using more complex techniques.
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further evidence to show population specificity of Discriminant Function equations for sex determination using the talus of south african blacks
Journal of Forensic Sciences, 2004Co-Authors: Mubarak A Bidmos, Manisha R DayalAbstract:Several studies have shown that osteometric differences exist between different population groups. Thus, Discriminant Function equations derived for the determination of sex from skeletal elements are population specific. In a previous study, the authors derived such equations from nine measurements of the talus of South African whites with high levels of average accuracies. The validity of some of the equations was tested on data collected from a South African black sample that consisted of 120 tali, equally distributed by sex, derived from the Raymond A. Dart Collection of Human Skeletons. The average accuracies dropped significantly. This necessitated the derivation of new equations for the South African black population and the average accuracies obtained ranged between 80% and 89%. The validity of the equations derived from the present study was tested using the leave-one-out classification and two independent samples (1 and 2). The applicability of the equations with very high classification rate from the present study was tested on Independent sample 1 of 10 white tali with poor results. The result of the validity of these equations on an Independent sample 2 of 10 black tali revealed acceptably high average accuracies in correct classification thereby supporting earlier observations on population specificity of Discriminant Function equations.
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Discriminant Function sexing of fragmentary femur of south african blacks
Forensic Science International, 2004Co-Authors: Samuel A Asala, Mubarak A Bidmos, Manisha R DayalAbstract:When fragmentary and incomplete bones are all that are available to the forensic anthropologist for use in sex determination, non-metric and metric sex discriminating parameters that have been derived from complete bones may be of little use. In such circumstances, sex discriminating metric methods that are of specific application to fragmentary bones will be more useful. Since such studies have not been systematically carried out in bones of South African blacks, the aim of this study was to begin to provide such data. Two hundred and twenty left femurs of black South Africans were obtained from the Raymond A. Dart Collection of African Skeleton, School of Anatomical Sciences, University of the Witwatersrand, South Africa. Five variables from the upper end of the femur and three variables from the lower end of the femur were measured and subjected to univariate and multivariate Discriminant Function analyses. The vertical head diameter and the medial condylar length were most successful in sex identification from the upper and lower ends of the femur respectively. The combined variables were more useful than the use of variables individually. Discriminant Function score equations were derived for individual and combined variables from the upper and lower ends of the femur of the South African blacks.
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sex determination from the talus of south african whites by Discriminant Function analysis
American Journal of Forensic Medicine and Pathology, 2003Co-Authors: Mubarak A Bidmos, Manisha R DayalAbstract:The field of forensic anthropology involves the building of an antemortem profile of an individual from skeletal remains. This includes sex and race determination and age and stature estimation. Since most bones that are conventionally used for sex determination are often recovered either in a fragmented or incomplete state, it has become necessary to use denser bones that are often recovered intact, eg, the patella, calcaneus, and talus. Thus the aim of this study is to assess the sex-determining ability of each of the measurements of the talus and derive Discriminant Function equations for sex determination in the South African white population. Sixty male and 60 female tali of South African whites obtained from the Raymond A. Dart Collection of Human Skeletons were used. Nine measurements were taken on each talus. Descriptive statistics and Discriminant Function analysis were performed on the acquired data. The basic statistics showed that all measurements were sexually dimorphic. Univariate, stepwise, and direct Discriminant Function equations were generated for use in sex determination. The level of average accuracy of sex classification was 80% to 82% for the univariate method, 85% to 88% for the stepwise method, and 81% to 86% for the direct method. It is concluded that the talus of South African whites is useful for sex determination.
Samuel A Asala - One of the best experts on this subject based on the ideXlab platform.
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Discriminant Function sexing of fragmentary femur of south african blacks
Forensic Science International, 2004Co-Authors: Samuel A Asala, Mubarak A Bidmos, Manisha R DayalAbstract:When fragmentary and incomplete bones are all that are available to the forensic anthropologist for use in sex determination, non-metric and metric sex discriminating parameters that have been derived from complete bones may be of little use. In such circumstances, sex discriminating metric methods that are of specific application to fragmentary bones will be more useful. Since such studies have not been systematically carried out in bones of South African blacks, the aim of this study was to begin to provide such data. Two hundred and twenty left femurs of black South Africans were obtained from the Raymond A. Dart Collection of African Skeleton, School of Anatomical Sciences, University of the Witwatersrand, South Africa. Five variables from the upper end of the femur and three variables from the lower end of the femur were measured and subjected to univariate and multivariate Discriminant Function analyses. The vertical head diameter and the medial condylar length were most successful in sex identification from the upper and lower ends of the femur respectively. The combined variables were more useful than the use of variables individually. Discriminant Function score equations were derived for individual and combined variables from the upper and lower ends of the femur of the South African blacks.
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Discriminant Function sexing of the calcaneus of the south african whites
Journal of Forensic Sciences, 2003Co-Authors: Mubarak A Bidmos, Samuel A AsalaAbstract:The skull and some postcranial elements, such as the humerus, femur, and tibia, have been used in their intact states for sex determination in forensic and archaeological cases. But, in practice, these bones are often recovered in fragmented states, which render them unsuitable for use in sex determination. The calcaneus is a compact bone that is able to withstand high tensile forces. Some of its parameters have been used for sex determination in American whites and blacks (1) and Italians (2). This bone has not been used for sex determination in the South African white population. Therefore, the aim of this study was to assess the degree of sexual dimorphism of the calcaneus of the South African white population sample, derive Discriminant Function score equations for use in sex determination, and determine the level of accuracy of its sex-determining ability. Nine parameters were measured on each pair of 53 male and 60 female calcanei of known South African white skeletons, obtained by a random sampling technique from the Raymond A. Dart Collection of Human Skeletons, School of Anatomical Sciences, University of the Witwatersrand, Johannesburg. Basic statistic and Discriminant Function analysis was performed on the acquired data. The basic statistics showed that all measured parameters were sexually dimorphic. Discriminant Function score equations were generated for use in sex determination. The average accuracy of sex classification ranged from 73 to 86% for the univariate method, 81 to 91% for the stepwise method, and 82 to 92% for the direct method. It is concluded that the calcaneus is useful for sex determination in the South African white population.
Shinichiro Omachi - One of the best experts on this subject based on the ideXlab platform.
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a new approximation method of the quadratic Discriminant Function
Lecture Notes in Computer Science, 2000Co-Authors: Shinichiro OmachiAbstract:For many statistical pattern recognition methods, distributions of sample vectors are assumed to be normal, and the quadratic Discriminant Function derived from the probability density Function of multivariate normal distribution is used for classification. However, the computational cost is O(n2) for n-dimensional vectors. Moreover, if there are not enough training sample patterns, covariance matrix can not be estimated accurately. In the case that the dimensionality is large, these disadvantages markedly reduce classification performance. In order to avoid these problems, in this paper, a new approximation method of the quadratic Discriminant Function is proposed. This approximation is done by replacing the values of small eigenvalues by a constant which is estimated by the maximum likelihood estimation. This approximation not only reduces the computational cost but also improves the classification accuracy.
Guy Lebreton - One of the best experts on this subject based on the ideXlab platform.
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one dimensional logarithmic harmonic synthetic Discriminant Function filters for shift scale and projection invariant pattern recognition
Optics Letters, 1998Co-Authors: Guy LebretonAbstract:We introduce a new approach for shift-, scale-, and projection-invariant pattern recognition that combines the harmonic expansion and the synthetic Discriminant Function approaches by use of a synthetic Discriminant Function filter with equal-order one-dimensional logarithmic harmonic components. Because projection invariance in one direction is guaranteed by the harmonics, the required number of training images is much fewer than with classical synthetic Discriminant Function filters.