Search results for "cross-validation"
showing 10 items of 50 documents
Sexing birds using discriminant function analysis: a critical appraisal.
2011
9 pages; International audience; Discriminant function analysis (DFA) based on morphological measurements is a quick, inexpensive, and efficient method for sex determination in field studies on cryptically monomorphic bird species. However, behind the apparent standardization and relative simplicity of DFA lie subtle differences and pitfalls that have been neglected in some studies. Most of these concerns directly affect assessment of the discriminant performance, a parameter of crucial importance in practice because it provides a measure of the quality of an equation that may be used in later field studies. Using results from 141 published studies and simulations based on a large data set …
Fishery-dependent and -independent data lead to consistent estimations of essential habitats
2016
AbstractSpecies mapping is an essential tool for conservation programmes as it provides clear pictures of the distribution of marine resources. However, in fishery ecology, the amount of objective scientific information is limited and data may not always be directly comparable. Information about the distribution of marine species can be derived from two main sources: fishery-independent data (scientific surveys at sea) and fishery-dependent data (collection and sampling by observers in commercial vessels). The aim of this paper is to compare whether these two different sources produce similar, complementary, or different results. We compare them in the specific context of identifying the Es…
Adjusted bat algorithm for tuning of support vector machine parameters
2016
Support vector machines are powerful and often used technique of supervised learning applied to classification. Quality of the constructed classifier can be improved by appropriate selection of the learning parameters. These parameters are often tuned using grid search with relatively large step. This optimization process can be done computationally more efficiently and more precisely using stochastic search metaheuristics. In this paper we propose adjusted bat algorithm for support vector machines parameter optimization and show that compared to the grid search it leads to a better classifier. We tested our approach on standard set of benchmark data sets from UCI machine learning repositor…
Mass Spectrometry Imaging Differentiates Chromophobe Renal Cell Carcinoma and Renal Oncocytoma with High Accuracy
2020
Background: While subtyping of the majority of malignant chromophobe renal cell carcinoma (cRCC) and benign renal oncocytoma (rO) is possible on morphology alone, additional histochemical, immunohistochemical or molecular investigations are required in a subset of cases. As currently used histochemical and immunohistological stains as well as genetic aberrations show considerable overlap in both tumors, additional techniques are required for differential diagnostics. Mass spectrometry imaging (MSI) combining the detection of multiple peptides with information about their localization in tissue may be a suitable technology to overcome this diagnostic challenge. Patients and Methods: Formalin…
A computational approach for the assessment of executive functions in patients with obsessive-compulsive disorder
2019
Previous studies on obsessive–compulsive disorder (OCD) showed impairments in executive domains, particularly in cognitive inhibition. In this perspective, the use of virtual reality showed huge potential in the assessment of executive functions; however, unfortunately, to date, no study on the assessment of these patients took advantage of the use of virtual environments. One of the main problems faced within assessment protocols is the use of a limited number of variables and tools when tailoring a personalized program. The main aim of this study was to provide a heuristic decision tree for the future development of tailored assessment protocols. To this purpose, we conducted a study that…
Probabilistic cross-validation estimators for Gaussian process regression
2018
Gaussian Processes (GPs) are state-of-the-art tools for regression. Inference of GP hyperparameters is typically done by maximizing the marginal log-likelihood (ML). If the data truly follows the GP model, using the ML approach is optimal and computationally efficient. Unfortunately very often this is not case and suboptimal results are obtained in terms of prediction error. Alternative procedures such as cross-validation (CV) schemes are often employed instead, but they usually incur in high computational costs. We propose a probabilistic version of CV (PCV) based on two different model pieces in order to reduce the dependence on a specific model choice. PCV presents the benefits from both…
Assessing positive body image, body satisfaction, weight bias, and appearance comparison in emerging adults: A cross-validation study across eight co…
2020
Positive body image refers to individuals' ability to conceptualize their bodies with love, respect, and appreciation. The study of positive body image is relatively new, and instruments used to investigate this multi-faceted construct have received limited use in non-English speaking countries. Thus, the aim of this investigation is to consider four measures that are associated with positive body image across eight different countries. Participants (n = 6272) completed the Body Appreciation Scale-2, the Body Areas Satisfaction Scale, the Physical Appearance Comparison Scale, and the Weight Bias Internalization Scale. Multi-group confirmatory factor analyses (MG-CFAs) and item-response theo…
From Vivaldi to Beatles and back: predicting lateralized brain responses to music.
2013
We aimed at predicting the temporal evolution of brain activity in naturalistic music listening conditions using a combination of neuroimaging and acoustic feature extraction. Participants were scanned using functional Magnetic Resonance Imaging (fMRI) while listening to two musical medleys, including pieces from various genres with and without lyrics. Regression models were built to predict voxel-wise brain activations which were then tested in a cross-validation setting in order to evaluate the robustness of the hence created models across stimuli. To further assess the generalizability of the models we extended the cross-validation procedure by including another dataset, which comprised …
Cross validation of the 1-mile walking test for men with mental retardation.
1997
The purpose of this study was to cross validate the equation developed by Rintala et al. (1992) to estimate the cardiorespiratory efficiency of men with mental retardation (MR). Subjects were 19 healthy men (27 ± 8 yr) with MR (IQ = 58 ± 12). Following familiarization, a graded maximal treadmill test and two 1-mile walk tests (Rockport Fitness Walking Test, RFWT) were administered. The peak VO 2 value was the criterion measure used to cross validate the equation. The equation was: Peak VO 2 (ml.kg -1 .min -1 ) = 101.92 - 2.356 (MILE) -0.420 (WEIGHT). The mean differences were 2.04 (MILE 1 )(P = 0.02) and 2.43 (MILE 2 )(P = 0.004) ml.kg -1 .min -1 . A significant positive correlation was fou…
Reliability and validity of the Newcastle Scales in relation to ICD-9-classification
1987
The assessment of endogenous depression by means of the Newcastle Scales (1965, 1971) has been validated by their correlation with biological findings in many previous studies. However, reliability and cross validation studies are lacking for these scales. We found the reliability of the Newcastle Scales to be sufficient or at least moderate in a sample of 70 inpatients with major depression. In order to cross validate both scales, the clinical classification according to ICD-9 and the assessment of the Newcastle Scales have been performed independently in a sample of 112 inpatients with Major Depressive Disorder (RDC). The rate of agreement between clinical diagnosis and classification acc…