Statistical Quality Criteria Research Articles

Disaggregating Racial and Ethnic Data: A Step Toward Diversity, Equity, and Inclusion

Disaggregating Racial and Ethnic Data: A Step Toward Diversity, Equity, and Inclusion

Utility of standard diffusion-weighted magnetic resonance imaging for the identification of ischemic optic neuropathy in giant cell arteritis

This study assessed diffusion abnormalities of the optic nerve (ON) in giant cell arteritis (GCA) patients with acute onset of visual impairment (VI) using diffusion-weighted magnetic resonance imaging (DWI). DWI scans of GCA patients with acute VI were evaluated in a case-control study. Two blinded neuroradiologists assessed randomized DWI scans of GCA and controls for ON restricted diffusion. Statistical quality criteria and inter-rater reliability (IRR) were calculated. DWI findings were compared to ophthalmological assessments. 35 GCA patients (76.2 ± 6.4 years; 37 scans) and 35 controls (75.7 ± 7.6 years; 38 scans) were included. ON restricted diffusion was detected in 81.1% (Reader 1) of GCA scans. Localization of ON restricted diffusion was at the optic nerve head in 80.6%, intraorbital in 11.1% and affecting both segments in 8.3%. DWI discerned affected from unaffected ON with a sensitivity, specificity, positive and negative predictive value of 87%/99%/96%/96%. IRR for ON restricted diffusion was κinter = 0.72 (95% CI 0.59–0.86). DWI findings challenged ophthalmologic diagnoses in 4 cases (11.4%). DWI visualizes anterior and posterior ON ischemia in GCA patients with high sensitivity and specificity, as well as substantial IRR. DWI may complement the ophthalmological assessment in patients with acute VI.

Questionnaire to Assess the Work-Related Orientation of Medical Rehabilitation from the Perspective of the Rehabilitants (WMR-R): Cross-Sectional Study Comparing the Short and Long Versions

The user perception of the work-related treatment is of great importance for the further development and success of work-related medical rehabilitation (WMR). The German Pension Insurance Fund (Deutsche Rentenversicherung DRV Bund) has therefore supported the development of the questionnaire WMR-R that can be used to assess the quality of the structure, process and results of work-related rehabilitation treatment from the patient's point of view. This paper presents a short version and compares it with the long version. Based on a representative sample stratified by indication, employed rehabilitants up to the age of 65 were randomly selected to be questioned 6 months after their rehabilitation with a long version (N=28276) or a short version (N=6611) of WMR-R. In addition, routine data of the German Pension Insurance Fund were included. 27 items each of the long version and 8 items of the short version are added up to a total score and compared with regard to test statistical quality criteria and sample sensitivity. Participation rates were slightly higher in the short version (31%, N=2115) than in the long version (28%, N=8019). The processing quality in both versions is comparable. The short and long versions correlate with each other at r=0.96 (p<0.01). Both versions have similar validity characteristics and separate well between WMR and standard rehabilitation. Both versions are robust to demographic, disease-related and socio-medical risk factors. Rehabilitants with addiction and psychosomatic as well as neurological diseases rate their rehabilitation as significantly more work-oriented compared to other indications, especially pneumology. Due to the low survey effort and the simple evaluation and interpretation, the short version is particularly suitable for routine surveys of WMR care quality. The long version allows a differentiated recording of the WMR offer of rehabilitation facilities in the sense of strength/weakness analyses.

Psychometrics of Art – Validation of RizbA, a Quantitative Rating Instrument for Pictorial Expression

ABSTRACT Although art has been subject to psychological research for some time, the artwork itself received little attention in quantitative research. The rating instrument for two-dimensional pictorial works (RizbA) fills this gap by providing a tool for formal picture analysis. This study validates the questionnaire on 294 images created by 147 non-artists. In an online test–retest study the material was rated by 880 (T1) and 475 (T2) experts in visual art using RizbA. Statistical quality criteria, Principal component analysis (PCA) and indices of factor similarity were computed. The overall test’s capacity of differentiation yields a partial eta-squared of .28 (T1) and .33 (T2). Test–retest reliability is .93. PCA reveals an eight-factors solution. Tucker’s coefficients of congruence range between |0.82| and |1.00|. Intraclass correlation coefficients are .81 (T1) and .84 (T2). Results indicate generalizability to nonprofessional art. As the first reliable tool for picture analysis, RizbA allows a more detailed examination of art and its correlates.

The Effect of Innovation Capabilities of Health Care Organizations on the Quality of Health Information Technology: Model Development With Cross-sectional Data

BackgroundLarge health organizations often struggle to build complex health information technology (HIT) solutions and are faced with ever-growing pressure to continuously innovate their information systems. Limited research has been conducted that explores the relationship between organizations’ innovative capabilities and HIT quality in the sense of achieving high-quality support for patient care processes.ObjectiveThe aim of this study is to explain how core constructs of organizational innovation capabilities are linked to HIT quality based on a conceptual sociotechnical model on innovation and quality of HIT, called the IQHIT model, to help determine how better information provision in health organizations can be achieved.MethodsWe designed a survey to assess various domains of HIT quality, innovation capabilities of health organizations, and context variables and administered it to hospital chief information officers across Austria, Germany, and Switzerland. Data from 232 hospitals were used to empirically fit the model using partial least squares structural equation modeling to reveal associations and mediating and moderating effects.ResultsThe resulting empirical IQHIT model reveals several associations between the analyzed constructs, which can be summarized in 2 main insights. First, it illustrates the linkage between the constructs measuring HIT quality by showing that the professionalism of information management explains the degree of HIT workflow support (R²=0.56), which in turn explains the perceived HIT quality (R²=0.53). Second, the model shows that HIT quality was positively influenced by innovation capabilities related to the top management team, the information technology department, and the organization at large. The assessment of the model’s statistical quality criteria indicated valid model specifications, including sufficient convergent and discriminant validity for measuring the latent constructs that underlie the measures of HIT quality and innovation capabilities.ConclusionsThe proposed sociotechnical IQHIT model points to the key role of professional information management for HIT workflow support in patient care and perceived HIT quality from the viewpoint of hospital chief information officers. Furthermore, it highlights that organizational innovation capabilities, particularly with respect to the top management team, facilitate HIT quality and suggests that health organizations establish this link by applying professional information management practices. The model may serve to stimulate further scientific work in the field of HIT adoption and diffusion and to provide practical guidance to managers, policy makers, and educators on how to achieve better patient care using HIT.

Giving the Art Greater weight in Art Psychology: RizbA, a Questionnaire for Formal Picture Analysis

Abstract In empirical art psychology and creativity research most studies focus on the psychological correlates of art. Only few go beyond treating artworks as categorical data (e.g. abstract vs. representational) and consider artworks in detail. In part this is due to the lack of reliable quantitative measurements. The rating instrument for two-dimensional pictorial works (RizbA) makes a difference to current research designs. The current study validates the questionnaire on a representative sample of contemporary visual art, consisting of 318 images depicting works by artists from different cultural areas dated to the 21st century. In a randomized test-retest design, the pictorial material was rated by 506 (T1) and 238 (T2) art experts using RizbA. Statistical quality criteria, such as item difficulty, capacity of differentiation, test-retest reliability, and intraclass correlation were calculated. Principal component analysis (PCA) and indices of factor similarity were computed. The overall test’s capacity for differentiation yields partial eta-squared of .31 (T1) and .40 (T2). Test-retest reliability is .86. PCA reveals an eight-factor solution, which is largely consistent across both measurement points. Tucker’s coefficient of congruence ranges between |.71| and |1.00|. Intraclass correlation coefficients are .86 (T1) and .73 (T2). This study indicates generalizability of the questionnaire to contemporary artworks. Although a conclusion on the factors’ structure cannot be drawn yet, results are very promising. As the first reliable quantitative tool for formal picture analysis, RizbA allows more detailedexamination of visual art and its psychological correlates. This broadens research methodology by giving art greater weight in art psychology and creativity research.

Standard Diffusion-weighted MRI for the Diagnosis of Central Retinal Artery Occlusion

PurposeTo evaluate diffusion abnormalities of the retina and optic nerve in patients with central retinal artery occlusion (CRAO) using standard stroke diffusion-weighted magnetic resonance imaging (DWI).MethodsIn this case-control study, DWI scans of patients with nonarteritic CRAO were retrospectively assessed for acute ischemia of the retina and optic nerve. Two neuroradiologists, blinded for patient diagnosis, randomly evaluated DWI of CRAO patients and controls (a collective of stroke and transient ischemic attack [TIA] patients) for restrictions of the retina and optic nerve. We calculated statistical quality criteria and analyzed inter-rater reliability using unweighted Kappa statistics.Results20 CRAO patients (60,6 ± 17 years) and 20 controls (60,7 ± 17 years) were included in the study. Sensitivity, specificity, positive and negative predictive values for retinal DWI restrictions were 75%/80%/79%/76% (reader 1) and 75%/100%/100%/80% (reader 2), respectively. Unweighted Kappa was κ = 0,70 (95% CI 0,48‑0,92), indicating “substantial” interrater reliability. In comparison, sensitivity, specificity, PPV and NPV (positive and negative predictive values) for restrictions of the optic nerve in CRAO were 55%/70%/65%/61% (reader 1) and 25%/100%/100%/57% (reader 2). Inter-rater reliability was “fair” with unweighted Kappa κ = 0,32 (95% CI 0,09‑0,56).ConclusionsRetinal diffusion restrictions were present in a majority of CRAO patients and detectable with reasonable sensitivity, high specificity and substantial inter-rater reliability. Further studies are necessary to study time dependency of retinal diffusion restrictions, improve image quality and investigate the reliability of retinal DWI to discern CRAO from other causes of acute loss of vision.

The Issue of Burnout and Work Satisfaction in Younger GPs-A Cluster Analysis Utilizing the HaMEdSi Study.

The shortage of general practitioners (GPs) in Germany has become a relevant problem. Therefore, it is important to find the determinants that make primary care more attractive, and which support GPs remaining in practice. Our aim in this exploratory study was to search for relevant GP subgroups and their characteristics in order to find starting points for improvements or interventions. We attempted a comprehensive survey of all GPs in the German region of Siegen-Wittgenstein with about 280,000 inhabitants. There were 158 GPs in the total population; 85 of these (53.8%) took part in the study. There were 64 male GPs (75.3%) in our sample. The mean age of the participants was 53.5 years (SD 8.93). The questionnaire was composed of demographic questions, questions regarding future perspectives, the Motivation for Medical Education Questionnaire (MoME-Q), the Maslach Burnout Inventory (MBI), and the Work Satisfaction Questionnaire. K-means cluster analyses were used for subgrouping. A 2-cluster solution had good statistical quality criteria. Cluster 1 was characterised by elderly GPs who more frequently had a resident physician in their practices. These GPs had low burnout scores and high work satisfaction scores. Cluster 2 consisted of younger GPs who less frequently had a resident in their practices. They had average burnout scores according to published norms and lower work satisfaction scores. There seems to be an age cohort effect regarding burnout and work satisfaction. Having a resident physician seems to be protective. Interventions should be designed for younger GPs, especially members of generation Y, to reduce burnout and improve work satisfaction.

Assessing Features of Psychometric Assessment Instruments: A Comparison of the COSMIN Checklist with Other Critical Appraisal Tools

The past 20 years have seen the development of instruments designed to specify standards and evaluate the adequacy of published studies with respect to the quality of study design, the quality of findings, as well as the quality of their reporting. In the field of psychometrics, the first minimum set of standards for the review of psychometric instruments was published in 1996 by the Scientific Advisory Committee of the Medical Outcomes Trust. Since then, a number of tools have been developed with similar aims. The present paper reviews basic psychometric properties (reliability, validity and responsiveness), compares six tools developed for the critical appraisal of psychometric studies and provides a worked example of using the COSMIN checklist, Terwee-m statistical quality criteria, and the levels of evidence synthesis using the method of Schellingerhout and colleagues (2012). This paper will aid users and reviewers of questionnaires in the quality appraisal and selection of appropriate instruments by presenting available assessment tools, their characteristics and utility.

DSS FOR IMPLEMENTING SYSTEMIC APPROACH TO FORECASTING

A computer based decision support system is proposed the basic tasks of which are modeling and forecasting of financial processes and credit risk estimation. The system is developed on the basis of system analysis principles, i.e. it has hierarchic architecture, there exists the possibility for taking into consideration some stochastic and information uncertainties, forming alternatives for models and forecasts, and tracking the computing procedures during all stages of data processing. A modular architecture is implemented that provides a possibility for the further easy enhancement and modification of the system functional possibilities with new forecasting and parameter estimation techniques, and the risk models. High quality of final result is achieved thanks to appropriate tracking of the computing procedures at all stages of data processing: preliminary data processing, model constructing, and forecasts estimation with appropriate sets of statistical quality criteria. Example is given for modeling selected processes and credit risk estimation. The example presented shows that the system developed has good perspectives for practical use.

Two maxentropic approaches to determine the probability density of compound risk losses

Here we present an application of two maxentropic procedures to determine the probability density distribution of a compound random variable describing aggregate risk, using only a finite number of empirically determined fractional moments. The two methods that we use are the Standard method of Maximum Entropy (SME) and the method of Maximum Entropy in the Mean (MEM). We analyze the performance and robustness of these two procedures in several numerical examples, in which the frequency of losses is Poisson and the individual losses are lognormal random variables. We shall verify that the reconstructions obtained pass a variety of statistical quality criteria, and provide good estimations of VaR and TVaR, which are important measures for risk management purposes. As side product of the work, we obtain a rather accurate numerical description of the density of such compound random variable.These approaches are also used to develop a procedure to determine the distribution of the individual losses from the knowledge of the total loss. Thus, if the only information available is the total loss, and the nature of the frequency of losses is known, the method of maximum entropy provides an efficient method to determine the individual losses as well.

Low Back Pain Patient Subgroups in Primary Care

In industrialized countries, low back pain (LBP) is one of the leading causes for prolonged sick leave, early retirement, and high health care costs. Providing the same treatments to all patients is neither effective nor feasible, and may impede patients' recovery. Recent studies have outlined the need for subgroup-specific treatment allocation. This is a cross-sectional study that used baseline data from consecutively recruited patients participating in a guideline implementation trial regarding LBP in primary care. Classification variables were employment status, age, pain intensity, functional capacity (HFAQ), depression (CES-D), belief that activity causes pain (FABQ subscale), 2 scales of the SF-36 (general health, vitality), and days in pain per year. We performed k-means cluster analyses and split-half cross-validation. Subsequently, we investigated whether the resulting groups incurred different direct and indirect costs during a 6-month period before the index consultation. A 4-cluster solution showed good statistical quality criteria, even after split-half cross-validation. "Elderly patients adapted to pain" (cluster 1) and "younger patients with acute pain" (cluster 4) accounted for 55% of all patients. Cluster validation showed the lowest direct and indirect costs in these groups. About 72% of total costs per patient referred to clusters 2 and 3 ("patients with chronic severe pain with comorbid depression" and "younger patients with subacute pain and emotional distress"). Our study adds substantially to the knowledge of LBP-related case-mix in primary care. Information on differential health care needs may be inferred from our study, enabling decision makers to allocate resources more appropriately and to reduce costs.

Two Maxentropic Approaches to Determine the Probability Density of Compound Risk Losses

Here we present an application of two maxentropic procedures to determine the probability density distribution of a compound random variable describing aggregate risk, using only a finite number of empirically determined fractional moments. The two methods that we use are the Standard method of Maximum Entropy (SME) and the method of Maximum Entropy in the Mean (MEM). We analyze the performance and robustness of these two procedures in several numerical examples, in which the frequency of losses is Poisson and the individual losses are lognormal random variables. We shall verify that the reconstructions obtained pass a variety of statistical quality criteria, and provide good estimations of VaR and TVaR, which are important measures for risk management purposes. As side product of the work, we obtain a rather accurate numerical description of the density of such compound random variable. These approaches are also used to develop a procedure to determine the distribution of the individual losses from the knowledge of the total loss. Thus, if the only information available is the total loss, and the nature of the frequency of losses is known, the method of maximum entropy provides an efficient method to determine the individual losses as well.

Fuzzy logic system based prediction effort: A case study on the effects of tire parameters on contact area and contact pressure

Various methodologies of artificial intelligence have been recently used for estimating performance parameters of soil working machines and off-road vehicles. Due to nonlinear and stochastic features of soil–wheel interactions, application of knowledge-based Mamdani max–min fuzzy expert system for estimation of contact area and contact pressure is described in this paper. Fuzzy logic model was constructed by use of the experience of contact area and contact pressure utilizing data obtained from series of experimentations in soil bin facility and a single-wheel tester. Two paramount tire parameters: wheel load and tire inflation pressure are the input variables for our model, each has five membership functions. As a fundamental aspect of the fuzzy logic based prediction systems, a set of fuzzy if-then rules were used in accordance with fuzzy logic principles. 25 linguistic if-then rules were included to develop a complicated highly intelligent predicting model based on Centroid method at defuzzification stage. The model performance was assessed on the basis of several statistical quality criteria. Mean relative error lower than 10%, satisfactory scattering around unity-slope line (T), and high coefficient of determination, R2, were obtained by the fuzzy logic model proposed in this study.

Practical Economic Statistical Design of ̅&lt;i&gt;X&lt;/i&gt; Chart

This paper developed an understandable economic mathematical model of total cost of quality related to the use of control chart. This model considers both statistical quality and cost criteria. The statistical quality constraints considered in this paper are type I error (α) and type II error (β). The total cost of quality is a function of sample size (n) and sampling frequency (f). The model of total cost can be optimized to determine values of n and f that minimize the total cost of quality, while quality level is satisfied. The model can be solved by common spreadsheet program. The economic statistical model is developed under the real situation of a case study company to make the model realistic.

Health-Related Quality of Life In Patients with Chronic Myeloid Leukemia: What Have We Learned Over the Last Twenty Years?.

AbstractAbstract 3423 Background:Ensuring the highest possible standards of health-related quality of life (HRQOL) in patients with CML is now one of the top priorities of clinical research. There are several examples of how HRQOL data have contributed in better understanding overall treatment effectiveness in patients diagnosed with cancer malignancies. However, no evidence exists regarding the amount and the quality HRQOL research conducted in CML patients. Aim:The main objective of this paper is to systematically review all evidence-base data available, published over the last twenty years, stemming from studies focusing on HRQOL and other patient-reported outcomes (PROs) in CML patients. Materials and Methods:A systematic review broadly following the Cochrane methodology was performed. A literature search was undertaken in a number of databases by two independent reviewers. The following databases were used: PubMed (1980- October 2009), Cumulative index of Nursing and Allied Health Literature (CINHAL), SCOPUS (1980-2009), PsycINFO and PsycARTICLES (1980-2009). Additional literature was identified via the reference lists of these articles and a search of references was also performed by hand. Key experts in the field of hematological research were contacted. Candidate articles were then also independently scrutinized for possible inclusion. Any original article including a HRQOL evaluation or any other type of PROs (according to the current definition by the Food and Drug Administration) was considered. Any study regardless of the treatment, design and type of analysis (quantitative or qualitative) was considered eligible. No restrictions in the number of patients enrolled was applied. All studies meeting the criteria were then independently evaluated by two reviewers on their methodological quality according to a previously developed protocol. This included a number of methodological and statistical quality criteria such as questionnaire used, timing of assessment, missing data documentation, and discussion of HRQOL outcomes in terms of clinical significance. Results:Over 350 articles were scrutinized for possible inclusion in the review and 15 met inclusion criteria. No studies were published before 1995 and 10 studies (67%) were published after year 2000. Six studies (40%) dealt with interferon (IFN) based-treatments, 7 (47%) with bone marrow transplantation (BMT) and 2 (13%) with targeted therapies. Only 5 (33%) studies included an overall sample of more than 100 CML patients thus providing more confidence on HRQOL analysis. The EORTC QLQ-C30 was the most frequently used HRQOL measure being employed in 4 (27%) studies. Evidence stemming from studies comparing IFN with conventional hydroxyurea or busulfan treatments highlighted major HRQOL impairment associated with IFN even in the long run. These were particularly evident in a number of functional areas: cognitive, social, and sexual functioning as well as for symptoms: fatigue, pain and dyspnea, nausea/vomiting, flu-like and febrile, skin problems. Neuropsychological limitations and mood disorders were also found to be associated with IFN based-therapy. As concern BMT, current evidence suggests that even in the long run (i.e. 10 years after transplantation) physical limitations are still evident when compared to age matched general population norms. Although two studies dealing with targeted therapies were found to have included a HRQOL component in the study design, only one fully documented HRQOL outcomes. This was a randomized controlled trial (IRIS Study) (HRQOL being used a secondary endpoint) showing a clear advantage in terms of HRQOL of Imatinib over IFN based therapy. The difference between treatment arms (IM vs. IFN) was not only statistically significant but also clinically meaningful and with a large effect size (ES=1.05). Conclusions:HRQOL evidence base data is scarce in CML patients. The main conclusion that can be drawn is that IM offer major advantages in terms of HRQOL compared with IFN based therapies. However, long-term HRQOL data of IM therapy are needed to determine the impact of therapy over the long run from the patients' perspective. We expect patient-reported HRQOL becoming more and more a crucial outcome to fully evaluate overall treatment effectiveness of future therapeutic approaches in this area. Disclosures:No relevant conflicts of interest to declare.

An easy‐to‐use Decoy Database Builder software tool, implementing different decoy strategies for false discovery rate calculation in automated MS/MS protein identifications

One of the major challenges for large scale proteomics research is the quality evaluation of results. Protein identification from complex biological samples or experimental setups is often a manual and subjective task which lacks profound statistical evaluation. This is not feasible for high-throughput proteomic experiments which result in large datasets of thousands of peptides and proteins and their corresponding mass spectra. To improve the quality, reliability and comparability of scientific results, an estimation of the rate of erroneously identified proteins is advisable. Moreover, scientific journals increasingly stipulate that articles containing considerable MS data should be subject to stringent statistical evaluation. We present a newly developed easy-to-use software tool enabling quality evaluation by generating composite target-decoy databases usable with all relevant protein search engines. This tool, when used in conjunction with relevant statistical quality criteria, enables to reliably determine peptides and proteins of high quality, even for nonexperienced users (e.g. laboratory staff, researchers without programming knowledge). Different strategies for building decoy databases are implemented and the resulting databases are characterized and compared. The quality of protein identification in high-throughput proteomics is usually measured by the false positive rate (FPR), but it is shown that the false discovery rate (FDR) delivers a more meaningful, robust and comparable value.

What Have We Learned from Measuring Health-Related Quality of Life in Patients with Chronic Lymphocytic Leukemia? A Systematic Review of Published Studies from 1990 to 2007.

While a large amount of health-related quality of life (HRQOL) studies has been conducted in patients with solid tumors, no data are available for patients with CLL. The aim of the present work was therefore to quantify and evaluate the quality of studies investigating patient's self-reported HRQOL in CLL patients. A systematic literature search for studies meeting the criteria, published from 1990 to 2007, was undertaken on a number of databases. Candidate articles were mainly searched in PubMed and the Cochrane Central Register of Controlled Trials (CENTRAL). Meeting abstracts at ASCO and ASH conferences were also assessed. We used the following key terms to identify candidate articles “quality of life” and “CLL” or “lymphocytic leukemia” or “chronic leukemia”. All articles included in the review were independently evaluated based on a pre-defined set of methodological issues and criteria by two reviewers (SM and FE). These included a number of methodological and statistical quality criteria such as HRQOL missing data documentation, timing of assessment, rationale for instrument selection and discussion of outcomes in terms of clinical significance. In addition, HRQOL and traditional clinical outcomes were extracted and analyzed. More than 200 candidate articles were evaluated, but only 5 studies met the inclusion criteria for the review. The majority of articles were excluded as HRQOL was not measured by patient's reported tools. Overall, some 1019 patients were involved in these studies. HRQOL was assessed in 3 prospective randomized controlled trials (RCTs) and 2 longitudinal non-randomized studies. Two of these 5 studies were only published as abstracts. The EORTC QLQ-C30 was the most frequently used measure being utilized in 4 out of 5 studies. Some methodological constraints were identified, mainly in terms of handling of HRQOL missing data and possible lack of sensitivity of the measure being used. The most robust evidence stemmed from a prospective RCT comparing Fludarabine (F) vs. Fludarabine + Cyclophopsphamide (FC) where HRQOL was assessed as a secondary endpoint. While there was no significant HRQOL difference between treatment arms over time, this study showed nonetheless that the newer FC combination had no detrimental effect on patient's HRQOL compared with the standard F arm. This information definitely reinforces concomitant clinical findings which favor the more intensive FC treatment (e.g. in terms of clinical response and progression-free survival). Taken together, very limited conclusions can to date be drawn with regard to HRQOL issues in patients with CLL in view of the paucity of data in this area. There is urgent need of implementing HRQOL research in patients with CLL and of providing the scientific community with robust evidence-based data on the impact of new treatment approaches in these patients.

Evaluating experimental methods and techniques in X-ray diffraction using 280 000 data sets in the Powder Diffraction File

Release 2003 of the Powder Diffraction File (PDF) contains ∼280 000 unique entries organized in a series of tables in a relational database format. The PDF is available in two products, PDF-4/Full File and PDF-4/Organics, which allow users to access and query over 150 million filled entry fields. An editorial database is used to generate the commercial products that contain tables of experimental details and statistical evaluation criteria used by the editors to evaluate quality and determine quality marks for each entry in the PDF. This editorial database has nearly doubled the searchable entry fields. This database was mined to evaluate experimental methods in X-ray diffraction. Both experimental powder diffraction data and data calculated from predominantly single crystal X-ray structural analyses were assigned statistical quality criteria. For experimental powder data, the average delta two theta values for all d-spacings in the entry set were used. Calculated data were evaluated using R factor values as the primary quality criteria. A Quality Index, which measures the errors in refined unit cell parameters divided by the magnitude of the cell parameter, can be used to compare all types of data. Experimental variables were then analyzed versus these criteria. Variables include optic configuration, (i.e., Seeman–Bohlin, Guinier, Debye–Scherrer), use of internal and external standards, use of monochromators, wavelength divergence, wavelength selection, equipment radius, specimen transparency, and specimen absorption. This study significantly differs from prior round robin analyses in that the use of the database allows us to study very large population sets for every variable analyzed.

Choice of Cost-Estimation Functions Based on Statistical Quality Criteria and Technical Coherence

This paper studies the problem of choosing cost estimation functions by mixing statistical regression criteria and technical coherence. The parametric cost estimation method which looks for functional relationship between cost driver variables and the product cost is particularly well adapted to early economic evaluation during the design phase; it is simple to implement, efficient, and reactive enough to provide a powerful guideline for the designer. These cost estimation relationships (CER) are generally computed using linear or nonlinear regression algorithms. However, the problem is to identify and to choose the best CER among several candidate formulae which have been developed. In many cases, the statistical regression quality and estimation criteria are not sufficient. It is also necessary to consider the technical coherence of the CER as defined by the experts in the application domain. Therefore, an additional problem is to make these different points of view consistent. In this paper, the authors adopt a weighted multicriteria decision approach. The characteristics of the different quality criteria are described, then three practical selection methods are presented. All these methods measure the general quality of CERs, taking into account both technical and statistical points of view. The methods are based on a measure of quality using a weighted sum of normalised criteria, a weighted ranking method, and an original use of a similarity measure in the criteria space. These methods are then tested and compared using a real case.