scholarly journals Performance Evaluation of Source Camera Attribution by Using Likelihood Ratio Methods

2021 ◽  
Vol 7 (7) ◽  
pp. 116
Author(s):  
Pasquale Ferrara ◽  
Rudolf Haraksim ◽  
Laurent Beslay
Keyword(s):  
Performance Evaluation ◽  
Likelihood Ratio ◽  
Performance Metrics ◽  
Error Rates ◽  
Decision Threshold ◽  
Source Attribution ◽  
Likelihood Ratios ◽  
Receiver Operating Characteristic Curves ◽  
Evidence Evaluation ◽  
Similarity Scores

Performance evaluation of source camera attribution methods typically stop at the level of analysis of hard to interpret similarity scores. Standard analytic tools include Detection Error Trade-off or Receiver Operating Characteristic curves, or other scalar performance metrics, such as Equal Error Rate or error rates at a specific decision threshold. However, the main drawback of similarity scores is their lack of probabilistic interpretation and thereby their lack of usability in forensic investigation, when assisting the trier of fact to make more sound and more informed decisions. The main objective of this work is to demonstrate a transition from the similarity scores to likelihood ratios in the scope of digital evidence evaluation, which not only have probabilistic meaning, but can be immediately incorporated into the forensic casework and combined with the rest of the case-related forensic. Likelihood ratios are calculated from the Photo Response Non-Uniformity source attribution similarity scores. The experiments conducted aim to compare different strategies applied to both digital images and videos, by considering their respective peculiarities. The results are presented in a format compatible with the guideline for validation of forensic likelihood ratio methods.

Diagnostic efficiency of four lactate dehydrogenase isoenzyme-1 ratios in serum after myocardial infarction.

1988 ◽  
Vol 34 (10) ◽  
pp. 1960-1965 ◽  
Author(s):  
J F Loughlin ◽  
P M Krijnen ◽  
G Jablonsky ◽  
F Y Leung ◽  
A R Henderson
Keyword(s):  
Myocardial Infarction ◽  
Chest Pain ◽  
Operating Characteristic ◽  
Decision Threshold ◽  
Diagnostic Efficiency ◽  
Threshold Values ◽  
Likelihood Ratios ◽  
Diagnostic Efficacy ◽  
Receiver Operating Characteristic Curves ◽  
Optimum Decision

Abstract We compared the diagnostic efficacy of the ratios LD-1/LD-2, LD-1/LD-3, LD-1/LD-4, and LD-1/LD-5 in 69 documented cases of myocardial infarction. We used 149 patients with congestive heart failure and 67 patients with nonmyocardial infarct as controls. We used a computer program to produce receiver-operating characteristic curves, decision threshold plots, and likelihood ratios for these LD ratios at 6-h intervals up to 108 h after the onset of chest pain or hospital admission. All ratios in the myocardial infarction cases peaked around 36 h after the onset of chest pain, while those for the nonmyocardial and congestive cardiac failure cases did not change over the 108-h period. In all patients with infarctions, LD-1/LD-4 and LD-1/LD-5 increased by 1.7 times (when LD-1 was less than 40%) and 3.4 times (when LD-1 was greater than 40%), respectively, over control values. Optimum decision threshold values were obtained at 13-24 h (LD-1/LD-5), 31-36 h (LD-1/LD-4 and LD-1/LD-3), and 55-60 h (LD-1/LD-2) after onset of symptoms. The highest likelihood ratio was obtained with the LD-1/LD-4 ratio; therefore, we suggest that this is a better diagnostic test for myocardial infarction than LD-1/LD-2.

scholarly journals Geometric Approach to Analytic Marginalisation of the Likelihood Ratio for Continuous Gravitational Wave Searches

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 174
Author(s):  
Karl Wette
Keyword(s):  
Gravitational Wave ◽  
Likelihood Ratio ◽  
Signal To Noise Ratio ◽  
Geometric Approach ◽  
The Other ◽  
Efficient Computation ◽  
Likelihood Ratios ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Optimal Signal

The likelihood ratio for a continuous gravitational wave signal is viewed geometrically as a function of the orientation of two vectors; one representing the optimal signal-to-noise ratio, and the other representing the maximised likelihood ratio or F-statistic. Analytic marginalisation over the angle between the vectors yields a marginalised likelihood ratio, which is a function of the F-statistic. Further analytic marginalisation over the optimal signal-to-noise ratio is explored using different choices of prior. Monte-Carlo simulations show that the marginalised likelihood ratios had identical detection power to the F-statistic. This approach demonstrates a route to viewing the F-statistic in a Bayesian context, while retaining the advantages of its efficient computation.

scholarly journals Value and Diagnostic Efficacy of Fetal Morphology Assessment Using Ultrasound in A Poor-Resource Setting

Diagnostics ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 109 ◽  
Author(s):  
Ukweh ◽  
Ugbem ◽  
Okeke ◽  
Ekpo
Keyword(s):  
Predictive Value ◽  
Performance Metrics ◽  
Area Under The Curve ◽  
Youden Index ◽  
Likelihood Ratios ◽  
Diagnostic Efficacy ◽  
Predictive Values ◽  
Resource Setting ◽  
Post Test ◽  
Sensitivity Specificity

Background: Ultrasound is operator-dependent, and its value and efficacy in fetal morphology assessment in a low-resource setting is poorly understood. We assessed the value and efficacy of fetal morphology ultrasound assessment in a Nigerian setting. Materials and Methods: We surveyed fetal morphology ultrasound performed across five facilities and followed-up each fetus to ascertain the outcome. Fetuses were surveyed in the second trimester (18th–22nd weeks) using the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) guideline. Clinical and surgical reports were used as references to assess the diagnostic efficacy of ultrasound in livebirths, and autopsy reports to confirm anomalies in terminated pregnancies, spontaneous abortions, intrauterine fetal deaths, and still births. We calculated sensitivity, specificity, positive and negative predictive values, Area under the curve (AUC), Youden index, likelihood ratios, and post-test probabilities. Results: In total, 6520 fetuses of women aged 15–46 years (mean = 31.7 years) were surveyed. The overall sensitivity, specificity, and AUC were 77.1 (95% CI: 68–84.6), 99.5 (95% CI: 99.3–99.7), and 88.3 (95% CI: 83.7–92.2), respectively. Other performance metrics were: positive predictive value, 72.4 (95% CI: 64.7–79.0), negative predictive value, 99.6 (95% CI: 99.5–99.7), and Youden index (77.1%). Abnormality prevalence was 1.67% (95% CI: 1.37–2.01), and the positive and negative likelihood ratios were 254 (95% CI: 107.7–221.4) and 0.23 (95% CI: 0.16–0.33), respectively. The post-test probability for positive test was 72% (95% CI: 65–79). Conclusion: Fetal morphology assessment is valuable in a poor economics setting, however, the variation in the diagnostic efficacy across facilities and the limitations associated with the detection of circulatory system anomalies need to be addressed.

scholarly journals Restrictive spirometric pattern and true pulmonary restriction in a general population sample aged 50 - 64 years

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Kjell Torén ◽  
Linus Schiöler ◽  
Jonas Brisman ◽  
Andrei Malinovschi ◽  
Anna-Carin Olin ◽  
...  
Keyword(s):  
General Population ◽  
Likelihood Ratio ◽  
Population Sample ◽  
Positive Likelihood Ratio ◽  
Negative Likelihood Ratio ◽  
Population Based ◽  
Forced Expiratory Volume ◽  
Likelihood Ratios ◽  
Volume Determination ◽  
Total Lung Volume

Abstract Background There is low diagnostic accuracy of the proxy restrictive spirometric pattern (RSP) to identify true pulmonary restriction. This knowledge is based on patients referred for spirometry and total lung volume determination by plethysmograpy, single breath nitrogen washout technique or gas dilution and selected controls. There is, however, a lack of data from general populations analyzing whether RSP is a valid proxy for true pulmonary restriction. We have validated RSP in relation to true pulmonary restriction in a general population where we have access to measurements of total lung capacity (TLC) and spirometry. Methods The data was from the Swedish CArdioPulmonary bioImage Study (SCAPIS Pilot), a general population-based study, comprising 983 adults aged 50–64. All subjects answered a respiratory questionnaire. Forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were obtained before and after bronchodilation. TLC and residual volume (RV) was recorded using a body plethysmograph. All lung function values are generally expressed as percent predicted (% predicted) or in relation to lower limits of normal (LLN). True pulmonary restriction was defined as TLC < LLN5 defined as a Z score < − 1.645, i e the fifth percentile. RSP was defined as FEV1/FVC ≥ LLN and FVC < LLN after bronchodilation. Specificity, sensitivity, positive and negative likelihood ratios were calculated, and 95% confidence intervals (CIs) were calculated. Results The prevalence of true pulmonary restriction was 5.4%, and the prevalence of RSP was 3.4%. The sensitivity of RSP to identify true pulmonary restriction was 0.34 (0.20–0.46), the corresponding specificity was 0.98 (0.97–0.99), and the positive likelihood ratio was 21.1 (11.3–39.4) and the negative likelihood ratio was 0.67 (0.55–0.81). Conclusions RSP has low accuracy for identifying true pulmonary restriction. The results support previous observations that RSP is useful for ruling out true pulmonary restriction.

scholarly journals Alanina aminotransferasa como marcador en el diagnóstico de síndrome metabólico y riesgo cardiovascular en niños con obesidad

2019 ◽  
Vol 36 (4) ◽  
pp. 253-8
Author(s):  
Ysel Cabrera ◽  
Melissa Martínez ◽  
Almendra Cabello ◽  
Almendra Cabello ◽  
Samuel Pereyra ◽  
...  
Keyword(s):  
Likelihood Ratio ◽  
Likelihood Ratios ◽  
Síndrome Metabólico

Objetivo: Evaluar la alanina aminotransferasa (ALT) como marcador en el diagnóstico de síndrome metabólico (SM) y riesgo cardiovascular (RCV) en niños con obesidad exógena.Materiales y métodos: Estudio transversal. Se incluyeron niños con obesidad exógena de 2 a 14 años, atendidos en la Unidad de Endocrinología Pediátrica del Hospital NacionalCayetano Heredia, entre el 2014 al 2018. Se definió enfermedad hepática no alcohólica (EHNA) considerando dos puntos de corte de ALT; en mujeres: >22,1U/L y >44U/L, en varones: >25,8U/L y >50U/L. Se definió SM según la Academia Americana de Pediatría y RCV con TG/HDL-C ≥3,5. Aplicamos Chi cuadrado, considerándose significativo p<0,05. Estimamos sensibilidad(S), especificidad (E) y likelihood ratios (LR). Resultados: Se incluyeron 347 niños obesos (54,7% varones). La frecuencia de EHNA fue de 23,1%. La sensibilidad y especificidad para el diagnóstico de SM con ALT >22,1U/L y >25,8U/L fue 79,4% y 37,6% respectivamente y, con ALT>44U/L y >50U/L fue 28,6% y 83,3%. La ALT con punto de corte mayor en conjunto con TG/HDL-C≥3,5 mostró una especificidad del 96,9% y un likelihood ratio + (LR+) de 6,7. Conclusión: La ALT con un punto de corte >44U/L en mujeres y >50U/L en varones, es un marcador bioquímico útil en la identificación de SM y riesgo cardiovascular en niños con obesidad exógena desde los primeros años de vida.

Probabilistic Evaluation of SMS Messages as Forensic Evidence

2013 ◽  
pp. 138-149
Author(s):  
Shunichi Ishihara
Keyword(s):  
Likelihood Ratio ◽  
Low Cost ◽  
Scientific Evidence ◽  
Short Message ◽  
Likelihood Ratios ◽  
Forensic Evidence ◽  
Probabilistic Evaluation ◽  
Popular Medium ◽  
Log Likelihood ◽  
Message Service

This study is one of the first likelihood ratio-based forensic text comparison studies in forensic authorship analysis. The likelihood-ratio-based evaluation of scientific evidence has started being adopted in many disciplines of forensic evidence comparison sciences, such as DNA, handwriting, fingerprints, footwear, voice recording, etc., and it is largely accepted that this is the way to ensure the maximum accountability and transparency of the process. Due to its convenience and low cost, short message service (SMS) has been a very popular medium of communication for quite some time. Unfortunately, however, SMS messages are sometimes used for reprehensible purposes, e.g., communication between drug dealers and buyers, or in illicit acts such as extortion, fraud, scams, hoaxes, and false reports of terrorist threats. In this study, the author performs a likelihood-ratio-based forensic text comparison of SMS messages focusing on lexical features. The likelihood ratios (LRs) are calculated in Aitken and Lucy’s (2004) multivariate kernel density procedure, and are calibrated. The validity of the system is assessed based on the magnitude of the LRs using the log-likelihood-ratio cost (Cllr). The strength of the derived LRs is graphically presented in Tippett plots. The results of the current study are compared with those of previous studies.

Database Benchmarks

2011 ◽  
pp. 950-954
Author(s):  
Jérôme Darmont
Keyword(s):  
Performance Evaluation ◽  
Decision Support ◽  
System Performance ◽  
Performance Metrics ◽  
Actual Behavior ◽  
Future Trends ◽  
Measurement Tools ◽  
Object Relational ◽  
Model Set ◽  
System Performance Evaluation

Performance measurement tools are very important, both for designers and users of Database Management Systems (DBMSs). Performance evaluation is useful to designers to determine elements of architecture, and, more generally, to validate or refute hypotheses regarding the actual behavior of a DBMS. Thus, performance evaluation is an essential component in the development process of well-designed and efficient systems. Users may also employ performance evaluation, either to compare the efficiency of different technologies before selecting a DBMS, or to tune a system. Performance evaluation by experimentation on a real system is generally referred to as benchmarking. It consists of performing a series of tests on a given DBMS to estimate its performance in a given setting. Typically, a benchmark is constituted of two main elements: a database model (conceptual schema and extension), and a workload model (set of read and write operations) to apply on this database, following a predefined protocol. Most benchmarks also include a set of simple or composite performance metrics such as response time, throughput, number of input/output, disk or memory usage, and so forth. The aim of this article is to present an overview of the major families of state-of-the-art database benchmarks, namely, relational benchmarks, object and object-relational benchmarks, XML benchmarks, and decision-support benchmarks; and to discuss the issues, tradeoffs, and future trends in database benchmarking. We particularly focus on XML and decision-support benchmarks, which are currently the most innovative tools that are developed in this area.

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