Characterization of human and instrument related measurement errors

Measurement is the act or the result of a quantitative comparison between a given quantity and a quantity of the same kind chosen as a unit. It is generally agreed that all measurements contain errors. In a measuring system where both a measuring instrument and a human being taking the measurement using a preset process, the measurement error could be due to the instrument, the process or the human being involved. The first part of the study is devoted to understanding the human errors in measurement. For that, selected person related and selected work related factors that could affect measurement errors have been identified. Though these are well known, the exact extent of the error and the extent of effect of different factors on human errors in measurement are less reported. Characterization of human errors in measurement is done by conducting an experimental study using different subjects, where the factors were changed one at a time and the measurements made by them recorded. From the pre‐experiment survey research studies, it is observed that the respondents could not give the correct answers to questions related to the correct values [extent] of human related measurement errors. This confirmed the fears expressed regarding lack of knowledge about the extent of human related measurement errors among professionals associated with quality. But in postexperiment phase of survey study, it is observed that the answers regarding the extent of human related measurement errors has improved significantly since the answer choices were provided based on the experimental study. It is hoped that this work will help users of measurement in practice to better understand and manage the phenomena of human related errors in measurement.

Technical instruments and conceptual definitions: theoretical and practical implications of the change on the definition of unemployment in Colombia

En junio de 2000 el Departamento Nacional de Estadística de Colombia adopto una nueva definición de medición de desempleo siguiendo los estándares sugeridos por la organización Internacional del Trabajo (OIT). El cambio de definición implico una reducción de la tasa de desempleo en cerca de dos puntos porcentuales. En este documento contrastamos la experiencia colombiana con otra experiencias internacionales, y analizamos las implicaciones empíricas y teóricas de este cambio de definición usando dos tipos de estimaciones cuantitativas: en la primera se contrasta las principales características de las diferentes categorías clasificadas según la definición nueva y vieja de desempleo (empleado, desempleado y fuera de la fuerza laboral) usando el algoritmo EM; en la segunda se pone a prueba la implicación del desempleo estructural y su relación con el perfil educacional de personas desempleadas y las características teóricas que enfrentan los estándares de la OIT en la definición de empleo.

Measurement Quality in Indicators of Compositions: a Compositional Multitrait-Multimethod Approach

Compositional data, also called multiplicative ipsative data, are common in survey research instruments in areas such as time use, budget expenditure and social networks. Compositional data are usually expressed as proportions of a total, whose sum can only be 1. Owing to their constrained nature, statistical analysis in general, and estimation of measurement quality with a confirmatory factor analysis model for multitrait-multimethod (MTMM) designs in particular are challenging tasks. Compositional data are highly non-normal, as they range within the 0-1 interval. One component can only increase if some other(s) decrease, which results in spurious negative correlations among components which cannot be accounted for by the MTMM model parameters. In this article we show how researchers can use the correlated uniqueness model for MTMM designs in order to evaluate measurement quality of compositional indicators. We suggest using the additive log ratio transformation of the data, discuss several approaches to deal with zero components and explain how the interpretation of MTMM designs di ers from the application to standard unconstrained data. We show an illustration of the method on data of social network composition expressed in percentages of partner, family, friends and other members in which we conclude that the faceto-face collection mode is generally superior to the telephone mode, although primacy e ects are higher in the face-to-face mode. Compositions of strong ties (such as partner) are measured with higher quality than those of weaker ties (such as other network members)

UV index measurement and model agreement: uncertainties and limitations

En les últimes dècades, l'increment dels nivells de radiació solar ultraviolada (UVR) que arriba a la Terra (principalment degut a la disminució d'ozó estratosfèric) juntament amb l'augment detectat en malalties relacionades amb l'exposició a la UVR, ha portat a un gran volum d'investigacions sobre la radiació solar en aquesta banda i els seus efectes en els humans. L'índex ultraviolat (UVI), que ha estat adoptat internacionalment, va ser definit amb el propòsit d'informar al públic general sobre els riscos d'exposar el cos nu a la UVR i per tal d'enviar missatges preventius. L'UVI es va definir inicialment com el valor màxim diari. No obstant, el seu ús actual s'ha ampliat i té sentit referir-se a un valor instantani o a una evolució diària del valor d'UVI mesurat, modelitzat o predit. El valor concret d'UVI està afectat per la geometria Sol-Terra, els núvols, l'ozó, els aerosols, l'altitud i l'albedo superficial. Les mesures d'UVI d'alta qualitat són essencials com a referència i per estudiar tendències a llarg termini; es necessiten també tècniques acurades de modelització per tal d'entendre els factors que afecten la UVR, per predir l'UVI i com a control de qualitat de les mesures. És d'esperar que les mesures més acurades d'UVI s'obtinguin amb espectroradiòmetres. No obstant, com que els costs d'aquests dispositius són elevats, és més habitual trobar dades d'UVI de radiòmetres eritemàtics (de fet, la majoria de les xarxes d'UVI estan equipades amb aquest tipus de sensors). Els millors resultats en modelització s'obtenen amb models de transferència radiativa de dispersió múltiple quan es coneix bé la informació d'entrada. No obstant, habitualment no es coneix informació d'entrada, com per exemple les propietats òptiques dels aerosols, la qual cosa pot portar a importants incerteses en la modelització. Sovint, s'utilitzen models més simples per aplicacions com ara la predicció d'UVI o l'elaboració de mapes d'UVI, ja que aquests són més ràpids i requereixen menys paràmetres d'entrada. Tenint en compte aquest marc de treball, l'objectiu general d'aquest estudi és analitzar l'acord al qual es pot arribar entre la mesura i la modelització d'UVI per condicions de cel sense núvols. D'aquesta manera, en aquest estudi es presenten comparacions model-mesura per diferents tècniques de modelització, diferents opcions d'entrada i per mesures d'UVI tant de radiòmetres eritemàtics com d'espectroradiòmeters. Com a conclusió general, es pot afirmar que la comparació model-mesura és molt útil per detectar limitacions i estimar incerteses tant en les modelitzacions com en les mesures. Pel que fa a la modelització, les principals limitacions que s'han trobat és la falta de coneixement de la informació d'aerosols considerada com a entrada dels models. També, s'han trobat importants diferències entre l'ozó mesurat des de satèl·lit i des de la superfície terrestre, la qual cosa pot portar a diferències importants en l'UVI modelitzat. PTUV, una nova i simple parametrització pel càlcul ràpid d'UVI per condicions de cel serens, ha estat desenvolupada en base a càlculs de transferència radiativa. La parametrització mostra una bona execució tant respecte el model base com en comparació amb diverses mesures d'UVI. PTUV ha demostrat la seva utilitat per aplicacions particulars com ara l'estudi de l'evolució anual de l'UVI per un cert lloc (Girona) i la composició de mapes d'alta resolució de valors d'UVI típics per un territori concret (Catalunya). En relació a les mesures, es constata que és molt important saber la resposta espectral dels radiòmetres eritemàtics per tal d'evitar grans incerteses a la mesura d'UVI. Aquest instruments, si estan ben caracteritzats, mostren una bona comparació amb els espectroradiòmetres d'alta qualitat en la mesura d'UVI. Les qüestions més importants respecte les mesures són la calibració i estabilitat a llarg termini. També, s'ha observat un efecte de temperatura en el PTFE, un material utilitzat en els difusors en alguns instruments, cosa que potencialment podria tenir implicacions importants en el camp experimental. Finalment, i pel que fa a les comparacions model-mesura, el millor acord s'ha trobat quan es consideren mesures d'UVI d'espectroradiòmetres d'alta qualitat i s'usen models de transferència radiativa que consideren les millors dades disponibles pel que fa als paràmetres òptics d'ozó i aerosols i els seus canvis en el temps. D'aquesta manera, l'acord pot ser tan alt dins un 0.1º% en UVI, i típicament entre menys d'un 3%. Aquest acord es veu altament deteriorat si s'ignora la informació d'aerosols i depèn de manera important del valor d'albedo de dispersió simple dels aerosols. Altres dades d'entrada del model, com ara l'albedo superficial i els perfils d'ozó i temperatura introdueixen una incertesa menor en els resultats de modelització.

A three-dimensional magnetometer for motion sensing of a balloon-carried atmospheric measurement package

An instrument is described which carries three orthogonal geomagnetic field sensors on a standard meteorological balloon package, to sense rapid motion and position changes during ascent through the atmosphere. Because of the finite data bandwidth available over the UHF radio link, a burst sampling strategy is adopted. Bursts of 9s of measurements at 3.6Hz are interleaved with periods of slow data telemetry lasting 25s. Calculation of the variability in each channel is used to determine position changes, a method robust to periods of poor radio signals. During three balloon ascents, variability was found repeatedly at similar altitudes, simultaneously in each of three orthogonal sensors carried. This variability is attributed to atmospheric motions. It is found that the vertical sensor is least prone to stray motions, and that the use of two horizontal sensors provides no additional information over a single horizontal sensor

Global estimates of snow water equivalent from passive microwave instruments: history, challenges and future developments

Snow properties have been retrieved from satellite data for many decades. While snow extent is generally felt to be obtained reliably from visible-band data, there is less confidence in the measurements of snow mass or water equivalent derived from passive microwave instruments. This paper briefly reviews historical passive microwave instruments and products, and compares the large-scale patterns from these sources to those of general circulation models and leading reanalysis products. Differences are seen to be large between the datasets, particularly over Siberia. A better understanding of the errors in both the model-based and measurement-based datasets is required to exploit both fully. Techniques to apply to the satellite measurements for improved large-scale snow data are suggested.

In-situ comparison of the NOy instruments flown in MOZAIC and SPURT

Two aircraft instruments for the measurement of total odd nitrogen (NOy) were compared side by side aboard a Learjet A35 in April 2003 during a campaign of the AFO2000 project SPURT (Spurengastransport in der Tropopausenregion). The instruments albeit employing the same measurement principle (gold converter and chemiluminescence) had different inlet configurations. The ECO-Physics instrument operated by ETH-Zürich in SPURT had the gold converter mounted outside the aircraft, whereas the instrument operated by FZ-Jülich in the European project MOZAIC III (Measurements of ozone, water vapour, carbon monoxide and nitrogen oxides aboard Airbus A340 in-service aircraft) employed a Rosemount probe with 80 cm of FEP-tubing connecting the inlet to the gold converter. The NOy concentrations during the flight ranged between 0.3 and 3 ppb. The two data sets were compared in a blind fashion and each team followed its normal operating procedures. On average, the measurements agreed within 7%, i.e. within the combined uncertainty of the two instruments. This puts an upper limit on potential losses of HNO3 in the Rosemount inlet of the MOZAIC instrument. Larger transient deviations were observed during periods after calibrations and when the aircraft entered the stratosphere. The time lag of the MOZAIC instrument observed in these instances is in accordance with the time constant of the MOZAIC inlet line determined in the laboratory for HNO3.

Challenging measurement of the (16)O+(27)Al elastic and inelastic angular distributions up to large angles

The (16)O+(27)Al elastic and inelastic angular distributions have been measured in a broad angular range (13 degrees < theta(lab) < 52 degrees) at about 100 MeV incident energy. The use of the MAGNEX large acceptance magnetic spectrometer and of the ray-reconstruction analysis technique has been crucial in order to provide, in the same experiment, high-resolution energy spectra and cross-section measurements distributed over more than seven orders of magnitude down to hundreds of nb/sr. (C) 2011 Elsevier B.V. All rights reserved.

A dedicated setup for the measurement of the electron transport parameters in gases at large electric fields

Electron transport parameters are important in several areas ranging from particle detectors to plasma-assisted processing reactors. Nevertheless, especially at high fields strengths and for complex gases, relatively few data are published. A dedicated setup has been developed to measure the electron drift velocity and the first Townsend coefficient in parallel plate geometry. An RPC-like cell has been adopted to reach high field strengths without the risk of destructive sparks. The validation data obtained with pure Nitrogen will be presented and compared to a selection of the available literature and to calculations performed with Magboltz 2 version 8.6. The new data collected in pure Isobutane will then be discussed. This is the first time the electron drift velocity in pure Isobutane is measured well into the saturation region. Good agreement is found with expectations from Magboltz. (C) 2009 Elsevier B.V. All rights reserved.

HRQOL and subjective well-being: noncomplementary forms of outcome measurement

This review considers some of the broad principles that concern quality of life assessment. These are discussed in relation to health-related quality of life (HRQOL) and the measurement of subjective well-being. It is argued that there are serious logical and methodological issues concerning HRQOL measurement, to the extent that the instruments may not be regarded as valid measures of life quality as this term is generally understood. It is recommended that HRQOL measurement be abandoned in favor of three separate forms of measurement as medical symptoms, subjective well-being and specific dimensions of psychological ill-being.

The measurement of attribution of blame in the self-service technology context

It is argued that attribution of blame (AoB) will differ in the Self-Service Technology (SST) context versus the interpersonal services context, due to the inherent elements of the SST environment, thereby making it a construct worthy of further research in the SST setting. This paper presents a first step in this pursuit by validating a multiple-item instrument of AoB in the SST context, which, to the researchers’ knowledge, has not been done previously. The paper comments on the surprising lack of valid, unidimensional instruments to measure each of the dimensions of AoB (locus, controllability and stability), even in the interpersonal services context. Preliminary results of a pre-test and pilot study support a three-dimensional measurement model of attribution of blame, in the SST setting.

Critical ethnography of the cross-cultural adaptation of HRQoL instruments

The thesis examines current approaches to the adaptation of health-related quality of life (HRQoL) instruments for cross-cultural research. The major conclusion is that nearly all existing HRQoL adaptation is based on simplistic processes that ignore relevant underlying disciplines including cognitive psychology, sociolinguistics, cultural anthropology, translation theory and survey research.

Not all roads lead to Rome - a review of quality of life measurement in diabetes

Aims Quality of life (QoL) is recognized widely as an important health outcome in diabetes, where the burden of selfmanagement places great demands on the individual. However, the concept of QoL remains ambiguous and poorly defined. The aim of our review is to clarify the measurement of QoL in terms of conceptualization, terminology and psychometric properties, to review the instruments that have been used most frequently to assess QoL in diabetes research and make recommendations for how to select measures appropriately.

Methods A systematic literature search was conducted to identify the ten measures most frequently used to assess QoL in diabetes research (including clinical trials) from 1995 to March 2008.

Results Six thousand and eight-five abstracts were identified and screened for instrument names. Of the ten instruments most frequently used to assess ‘QoL’, only three actually do so [i.e. the generic World Health Organization Quality of Life (WHOQOL) and the diabetes-specific Diabetes Quality of Life (DQOL) and Audit of Diabetes-Dependent Quality of Life (ADDQoL)]. Seven instruments more accurately measure health status [Short-Form 36 (SF-36), EuroQoL 5-Dimension (EQ-5D)], treatment satisfaction [Diabetes Treatment Satisfaction Questionnaire (DTSQ)] and psychological well-being [Beck Depression Inventory (BDI), Hospital Anxiety and Depression Scale (HADS), Well-Being Questionnaire (W-BQ), Problem Areas in Diabetes (PAID)].

Conclusions No single measure can suit every purpose or application but, when measures are selected inappropriately and data misinterpreted, any conclusions drawn are fundamentally flawed. If we value QoL as a therapeutic goal, we must ensure that the instruments we use are both valid and reliable. QoL assessment has the proven potential to identify ways in which treatments can be tailored to reduce the burden of diabetes. With careful consideration, appropriate measures can be selected and truly robust assessments undertaken successfully.

Quality of life in restless legs syndrome: A systematic review of clinical trials and a critical review of instruments

Restless legs syndrome (RLS) is a neurological movement disorder characterized by sensory symptoms and motor disturbances. While the underlying cause remains unknown, it is suggested that 20–25% of people with RLS are affected seriously enough to require pharmacological treatment. Dopamine agonists (DAs) are the most common treatment and act by increasing the low levels of dopamine to which RLS is often attributed. A growing literature highlights the debilitating and distressing nature of this condition from the patient's perspective. While sleep problems are most commonly reported, the impact of RLS on quality of life (QOL) is wide ranging, affecting relationships with partners, sex life, family life, social life, leisure activities, friendships, everyday activities, concentration, travel, career/work, sleep, and health.

We conducted a systematic review of clinical trials in which DAs have been evaluated in terms of RLS-specific QOL, i.e. their impact on the QOL of people with RLS, and critically reviewed the development history and measurement properties of RLS-specific QOL instruments.

A systematic search using terms synonymous with RLS, DAs and QOL was conducted using Scopus software, which includes MEDLINE, PsycINFO, EMBASE, and CINAHL. Our search covered publications from 2000 (prior to which RLS-specific QOL measures did not exist) to August 2009. Trials were included in our review if they evaluated DAs for the treatment of adults with RLS and reported evaluation using an RLS-specific QOL measure. We also ran citation searches to identify papers reporting the development history and measurement properties of the identified RLS-specific QOL instruments.

Three measures of RLS-specific QOL have been developed in recent years and are reviewed here: the Restless Legs Syndrome Quality of Life (RLSQOL) questionnaire, the Restless Legs Syndrome Quality of Life Instrument (RLS-QLI), and the Quality of Life Restless Legs Syndrome (QOL-RLS) measure. Critical review indicates that each has limitations (particularly in terms of published developmental history and content validity). Eleven trials of DAs were identified that included assessment of RLS-specific QOL (nine using the RLSQOL and two using the QOL-RLS). In all studies, significant improvements in RLS-specific QOL were observed, although these were mostly short term (12 weeks) and large placebo effects were also noted.

In people with RLS, the use of DAs has been shown to improve RLS-specific QOL. Longer-term, large-scale studies may be needed to confirm these findings and demonstrate statistically significant improvements in RLS-specific QOL at lower doses. Further development of the RLS-specific QOL measures is needed to ensure that the full impact of RLS (and the full benefit of new treatments) on aspects of life identified as important to individuals is captured in future studies.

Medication adherence self-report instruments : implications for practice and research

Background: After an acute cardiac event, adhering to recommendations for pharmacologic therapy is important in achieving optimal health outcomes. Considering the impressive evidence base for cardiovascular pharmacotherapy, strategies for promoting adherence are less well developed. Furthermore, accessing reliable, valid, and cost-effective mechanisms of monitoring adherence in the research and clinical settings is challenging. Aim: The aim of this article was to review published self-report measures assessing and monitoring medication adherence in cardiovascular disease and provide recommendations for research into medication adherence. Methods: The electronic databases CINAHL, Medline, and Science Direct were searched using the key search terms medication adherence and/or compliance, cardiovascular, self-report measures, and questionnaires. The World Wide Web was searched using the Google and Google Scholar search engines, and reference lists of retrieved documents were reviewed. The search strategy was verified by a health librarian. Instruments were included if they specifically addressed medication adherence as a discrete construct rather than a disease-specific or a generic health status measurement. Findings: Despite of the problems with medication adherence identified in the literature, only 7 instruments met the search criteria. There was limited use of instruments across studies and settings to enable comparison across populations and extensive psychometric evaluation. Conclusions: Medication adherence is a complex, multifaceted construct dependent on a range of physical, social, economic, and psychological considerations. In spite of the importance of adherence in ensuring optimal cardiovascular outcomes, conceptual underpinnings and methods of assessing medication adherence require further discussion and debate.