Potential Sources Of Measurement Error Research Articles

New Estimates on Educational Attainment Using a Continuous Approach (1970–2010)

Summary In this paper we introduce a new set of estimates on educational attainment and inequality measures of education for 142 countries over the period 1970–2010. Most of the previous attempts to measure educational attainment have treated education as a categorical variable, whose mean is computed as a weighted average of the official duration of each cycle and attainment rates, thus omitting differences in educational achievement within levels of education. This aggregation into different groups may result in a loss of information, introducing, therefore, a potential source of measurement error. We explore here a more nuanced alternative to estimate educational attainment, which considers the continuous nature of education. This “continuous approach” allows us to impose more plausible assumptions about the distribution of years of schooling within each level of education, and to take into account the right censoring of the data in the estimation, thus leading to more accurate estimates of educational attainment and education inequality. These improved estimates may help to better understand the role of education on different aspects of development.

Assessing the Reliability of Performance Assessment Scores: Some Considerations in Selecting an Appropriate Framework.

Assessing the Reliability of Performance Assessment Scores: Some Considerations in Selecting an Appropriate Framework.

The Effect of Data Availability in Measuring Fund Managerss After-Tax Alpha

We examine potential sources of measurement error when evaluating the after-tax performance of fund managers based on periodic snapshots of their holdings alone, compared to when daily transactions data are also available. To do this, we compare portfolio return estimates based on imputed trades from monthly, quarterly and semi-annual snapshots with estimates that also incorporate daily trades for a sample of active institutional equity portfolios. This method allows us to directly measure the contribution of interim trading before-tax, while more accurately estimating the tax effects associated with turnover through observing actual trade prices. Further, availability of both trade and holdings data permits the identification of how contributions and tax effects arise from income and capital gains sources, as well as how they vary across investment styles and market conditions.

Measurement error in CT assessment of appendix diameter.

Appendiceal diameter continues to be cited as an important criterion for diagnosis of appendicitis by computed tomography (CT). To assess sources of error and variability in appendiceal diameter measurements by CT. In this institutional review board-approved review of imaging and medical records, we reviewed CTs performed in children <18years of age between Jan. 1 and Dec. 31, 2010. Appendiceal diameter was measured in the axial and coronal planes by two reviewers (R1, R2). One year later, 10% of cases were remeasured. For patients who had multiple CTs, serial measurements were made to assess within patient variability. Measurement differences between planes, within and between reviewers, within patients and between CT and pathological measurements were assessed using correlation coefficients and paired t-tests. Six hundred thirty-one CTs performed in 519 patients (mean age: 10.9 ± 4.9years, 50.8% female) were reviewed. Axial and coronal measurements were strongly correlated (r = 0.92-0.94, P < 0.0001) with coronal plane measurements significantly larger (P < 0.0001). Measurements were strongly correlated between reviewers (r = 0.89-0.9, P < 0.0001) but differed significantly in both planes (axial: +0.2mm, P=0.003; coronal: +0.1mm, P=0.007). Repeat measurements were significantly different for one reviewer only in the axial plane (0.3mm difference, P<0.05). Within patients imaged multiple times, measured appendix diameters differed significantly in the axial plane for both reviewers (R1: 0.5mm, P = 0.031; R2: 0.7mm, P = 0.022). Multiple potential sources of measurement error raise concern about the use of rigid diameter cutoffs for the diagnosis of acute appendicitis by CT.

A Two-Factor Model Better Explains Heterogeneity in Negative Symptoms: Evidence from the Positive and Negative Syndrome Scale.

Acknowledging separable factors underlying negative symptoms may lead to better understanding and treatment of negative symptoms in individuals with schizophrenia. The current study aimed to test whether the negative symptoms factor (NSF) of the Positive and Negative Syndrome Scale (PANSS) would be better represented by expressive and experiential deficit factors, rather than by a single factor model, using confirmatory factor analysis (CFA). Two hundred and twenty individuals with schizophrenia spectrum disorders completed the PANSS; subsamples additionally completed the Brief Negative Symptom Scale (BNSS) and the Motivation and Pleasure Scale—Self-Report (MAP-SR). CFA results indicated that the two-factor model fit the data better than the one-factor model; however, latent variables were closely correlated. The two-factor model’s fit was significantly improved by accounting for correlated residuals between N2 (emotional withdrawal) and N6 (lack of spontaneity and flow of conversation), and between N4 (passive social withdrawal) and G16 (active social avoidance), possibly reflecting common method variance. The two NSF factors exhibited differential patterns of correlation with subdomains of the BNSS and MAP-SR. These results suggest that the PANSS NSF would be better represented by a two-factor model than by a single-factor one, and support the two-factor model’s adequate criterion-related validity. Common method variance among several items may be a potential source of measurement error under a two-factor model of the PANSS NSF.

The Impact of Errors on PACER Test Healthy Fitness Zone Classification in Students

PURPOSE: In light of the current disease trends (obesity, diabetes, etc.) in children and adolescents a greater effort has been made for physical education classes to move away from sports skill-based programming to health, wellness, and fitness-based approaches. Accompanying this transition has been the implementation of physical fitness assessments that utilize evidence-based standards that measure physical fitness levels as related to good overall health. The PACER Test (FITNESSGRAM®) is a common fitness assessment that assesses cardiorespiratory fitness/aerobic capacity in children and adolescents. While the protocol and test administration is relatively straight forward, in large groups/classroom settings there can be potential sources of measurement error leading to miss counts and recording of PACER laps. The extent to which these errors affect the health risk classification of students is unknown, therefore the purpose of this study was to examine the impact PACER test recording error has on the health risk classification of students. METHODS: A sample of 528 students (272 males and 256 females), with an average age of 13.2 ± 2.5 yrs, and average BMI of 21.47 ± 4.7, from a large Midwestern school district participated in this project. Data from the PACER Test (FITNESSGRAM®) was adjusted by ±1 and ±2 laps to simulate counting and recording errors that may accompany PACER test administration. RESULTS: Results indicated 64.96% of students were classified in a healthy fitness zone (HFZ), 18.18% were classified as needing improvement (NI), and 16.86% were classified as needing improvement and having health risks (NI-HR). When accounting for lap count error the NI-HR classification saw the greatest percent change (+1: -11.24%, +2: -21.35%, -1: 10.11%, -2: 20.22%). CONCLUSIONS: The study showed that error in data collection of students affects those who need the most intervention to improve their physical fitness. This emphasizes the importance of accurate data collection of fitness tests in physical education classes.

A method of spatial correction for acoustic positioning biotelemetry

It has been stated that there is a certain amount of intrinsic error inherent in all remote sensing methods, including acoustic telemetry, which has gained popularity in both freshwater and marine environments to record fine-scale movements over small spatial scales. We performed stationary tag trials on three freshwater lakes where we placed transmitters at known locations around the lakes and used radio-acoustic positioning and telemetry (RAPT) system-derived location data to assess the measurement and systematic biases of the system. We used a geostatistical technique called ordinary kriging to deal with the systematic errors and a state-space model to represent the measurement error of the data. Furthermore, we applied the kriging correction and a continuous-time correlated random walk model in a state-space framework to predict locations of a lake trout. The stationary tagging trials produced a complex pattern of spatial error within each lake that could not properly be accounted for by a simple filtering process. Using fivefold cross-validation, positioning error was reduced from 93 to 99 % in three small lakes. We also identified tag depth as a potential source of measurement error. The application of a state-space model resulted in the contraction of home ranges of lake trout by 10–32 % and a 3–32 % reduction in total distance travelled. Our results indicate that the systematic biases were a greater source of error than the measurement errors using a RAPT system. Consequently, the addition of a state-space model had relatively little effect on the quality of the spatial correction compared with the kriging method. The kriging method was able to compensate for the systematic biases produced by the RAPT systems and in turn increased the quality of data returned.

Effects of repetitive pulsing on multi-kHz planar laser-induced incandescence imaging in laminar and turbulent flames.

Planar laser-induced incandescence (LII) imaging is reported at repetition rates up to 100kHz using a burst-mode laser system to enable studies of soot formation dynamics in highly turbulent flames. To quantify the accuracy and uncertainty of relative soot volume fraction measurements, the temporal evolution of the LII field in laminar and turbulent flames is examined at various laser operating conditions. Under high-speed repetitive probing, it is found that LII signals are sensitive to changes in soot physical characteristics when operating at high laser fluences within the soot vaporization regime. For these laser conditions, strong planar LII signals are observed at measurement rates up to 100kHz but are primarily useful for qualitative tracking of soot structure dynamics. However, LII signals collected at lower fluences allow sequential planar measurements of the relative soot volume fraction with a sufficient signal-to-noise ratio at repetition rates of 10-50kHz. Guidelines for identifying and avoiding the onset of repetitive probe effects in the LII signals are discussed, along with other potential sources of measurement error and uncertainty.

Improving qPCR telomere length assays: Controlling for well position effects increases statistical power.

Telomere length (TL) is commonly measured using quantitative PCR (qPCR). Although, easier than the southern blot of terminal restriction fragments (TRF) TL measurement method, one drawback of qPCR is that it introduces greater measurement error and thus reduces the statistical power of analyses. To address a potential source of measurement error, we consider the effect of well position on qPCR TL measurements. qPCR TL data from 3,638 people run on a Bio-Rad iCycler iQ are reanalyzed here. To evaluate measurement validity, correspondence with TRF, age, and between mother and offspring are examined. First, we present evidence for systematic variation in qPCR TL measurements in relation to thermocycler well position. Controlling for these well-position effects consistently improves measurement validity and yields estimated improvements in statistical power equivalent to increasing sample sizes by 16%. We additionally evaluated the linearity of the relationships between telomere and single copy gene control amplicons and between qPCR and TRF measures. We find that, unlike some previous reports, our data exhibit linear relationships. We introduce the standard error in percent, a superior method for quantifying measurement error as compared to the commonly used coefficient of variation. Using this measure, we find that excluding samples with high measurement error does not improve measurement validity in our study. Future studies using block-based thermocyclers should consider well position effects. Since additional information can be gleaned from well position corrections, rerunning analyses of previous results with well position correction could serve as an independent test of the validity of these results.

Multisensor data fusion via Gaussian process models for dimensional and geometric verification

An increasing amount of commercial measurement instruments implementing a wide range of measurement technologies is rapidly becoming available for dimensional and geometric verification. Multiple solutions are often acquired within the shop-floor with the aim of providing alternatives to cover a wider array of measurement needs, thus overcoming the limitations of individual instruments and technologies.In such scenarios, multisensor data fusion aims at going one step further by seeking original and different ways to analyze and combine multiple measurement datasets taken from the same measurand, in order to produce synergistic effects and ultimately obtain overall better measurement results.In this work an original approach to multisensor data fusion is presented, based on the development of Gaussian process models (the technique also known as kriging), starting from point sets acquired from multiple instruments. The approach is illustrated and validated through the application to a simulated test case and two real-life industrial metrology scenarios involving structured light scanners and coordinate measurement machines.The results show that not only the proposed approach allows for obtaining final measurement results whose metrological quality transcends that of the original single-sensor datasets, but also it allows to better characterize metrological performance and potential sources of measurement error originated from within each individual sensor.

Concordance of risk behavior reporting within HCV serodiscordant injecting partnerships of young injection drug users in San Francisco, CA

IntroductionYoung injection drug users (IDU, under age 30) often inject with other IDU, creating an environment for risk of blood-borne disease transmission through sharing of needles and drug preparation equipment. Epidemiologic studies rely on self reported injection behavior data for measures of transmission risk, therefore we sought to quantify the degree of concordance of reported injecting risk behaviors between injecting dyads. MethodsFrom May, 2006 through 2013 we enrolled 72 injecting dyads in San Francisco, California, who were hepatitis C virus (HCV) RNA discordant. Each partnership was followed prospectively for up to six months. Monthly interviews from each partner were date-matched and responses to relationship characteristics and risk behavior questions were compared. Concordance of reporting was estimated with the concordance correlation coefficient for longitudinal data (CCC) and the prevalence adjusted bias adjusted kappa (PABAK). ResultsParticipants had a median age of 26 (IQR: 23, 28) years and median years injecting of 7.0 (IQR: 3.0, 10.6). Thirty-eight percent of the injecting dyads were also sexual partners. Concordance levels were highest for partnership characteristics, such as length of acquaintance, number of days cohabitating, and sexual intercourse in the past month (CCC=0.95; 0.82, and 0.90, respectively). Shared injection risk behaviors such as injecting with the HCV+ partner's previously used syringe and using contaminated injection preparation equipment had slight to fair agreement (CCC=0.22; 0.23; PABAK=0.43, 0.36, respectively). ConclusionsConcordance levels ranged from low to high. Potential sources of measurement error for low agreement items include recall and social-desirability biases and question interpretation.

Unconstrained estimates of the equity risk premium

Estimates of the equity risk premium implied by analyst forecasts—generally 2–4 %—are often significantly below realized equity returns of 6 %. Measurement error could result from conservative assumptions, reliance upon consensus rather than detailed forecasts, the use of market rather than target prices, and regression analysis, which can be influenced by a small number of observations. We address these potential sources of measurement error. Our estimates are consistent with subsequently realized returns and capture systematic risk exposure. Alternative techniques could capture another form of priced risk or identify firm characteristics associated with systematic mispricing. From 1999 to 2008, we estimate an average equity risk premium in the United States of 5.3 %. The estimate increases from 3.1 % for 1999–2000 to 5.9 % from 2001 to 2008, comparable to the historical average of realized equity returns.

Inter-Rater Reliability: Comparison of Checklist and Global Scoring for OSCEs

Objective Structured Clinical Examinations (OSCEs) have been used globally in evaluating clinical competence in the education of health professionals. Despite the objective intent of OSCEs, scoring methods used by examiners have been a potential source of measurement error affecting the precision with which test scores are determined. In this study, we investigated the differences in the inter-rater reliabilities of objective checklist and subjective global rating scores of examiners (who were exposed to an online training program to standardise scoring techniques) across two medical schools. Examiners’ perceptions of the e-scoring program were also investigated. Two Australian universities shared three OSCE stations in their end-of-year undergraduate medical OSCEs. The scenarios were video-taped and used for on-line examiner training prior to actual exams. Examiner ratings of performance at both sites were analysed using generalisability theory. A single facet, all random persons by raters design [PxR] was used to measure inter-rater reliability for each station, separate for checklist scores and global ratings. The resulting variance components were pooled across stations and examination sites. Decision studies were used to measure reliability estimates. There was no significant mean score difference between examination sites. Variation in examinee ability accounted for 68.3% of the total variance in checklist scores and 90.2% in global ratings. Rater contribution was 1.4% & 0% of the total variance in checklist score and global rating respectively, reflecting high inter-rater reliability of the scores provided by co-examiners across the two schools. Score variance due to interaction and residual error was larger for checklist scores (30.3% vs 9.7%) than for global ratings. Reproducibility coefficients for global ratings were higher than for checklist scores. Survey results showed that the e-scoring package facilitated consensus on scoring techniques. This approach to examiner training also allowed examiners to calibrate the OSCEs in their own time. This study revealed that inter-rater reliability was higher for global ratings than for checklist scores, thus providing further evidence for the reliability of subjective examiner ratings.

Creative accounting or creative destruction? Firm-level productivity growth in Chinese manufacturing

We present the first comprehensive set of firm-level total factor productivity (TFP) estimates for China's manufacturing sector that spans China's entry into the WTO. For our preferred estimate, which adjusts for a number of potential sources of measurement error and bias, the weighted average annual productivity growth for incumbents is 2.85% for a gross output production function and 7.96% for a value added production function over the period 1998–2007. This is among the highest compared to other countries. Productivity growth at the industry level is even higher, reflecting the dynamic force of creative destruction. Over the entire period, net entry accounts for over two thirds of total TFP growth. In contrast to earlier studies looking at total non-agriculture including services, we find that TFP growth dominates input accumulation as a source of output growth.

Salivary flow and alpha-amylase: Collection technique, duration, and oral fluid type

There has been renewed interest in salivary alpha-amylase (sAA), a surrogate marker of autonomic/sympathetic activity, in biosocial research on stress vulnerability, reactivity, and recovery. This study explored the impact of saliva flow rate on sAA measurement by examining the influence of (1) the technique used to collect oral fluid—synthetic swab, cotton pledget, hydrocellulose microsponge, or passive drool; (2) collection point duration––the length of time the technique is employed (1–5 min); and (3) oral fluid type––whole unstimulated saliva (not absorbed by any material) or oral fluid sampled from areas near the parotid, submandibular, or sublingual salivary glands. sAA activity (U/mL) was the highest in oral fluid collected from the parotid and submandibular gland areas. The volume (mL) of oral fluid collected increased, and the activity of sAA (U/mL) decreased, as collection point duration lengthened. The magnitude of these effects varied according to collection technique and oral fluid type. Across all conditions, there were positive correlations (range .70–.88) between sAA activity (U/mL) and sAA output (U/min). Management of these potential sources of measurement error will be essential to ensuring the success of future research on the correlates and concomitants of sAA activity, stress-related reactivity and recovery, and diurnal variation.

Computing airfare elasticities or opening Pandora's box

Airfare elasticities are crucial for policy instruments for the stakeholders of tourism industry. Modellers attempting to estimate these elasticities face several challenges in the absence of microeconomic data on consumer preferences. The aim of this paper is to offer a critical analysis of the practice of computing airfare elasticities from tourism demand studies. It identifies and discusses potential sources of measurement errors in the data and drawbacks that investigators face and assesses their implications for the estimated parameters in the respective models. The use of price of crude oil and distance between origin and destination as proxies for transportation costs are evaluated. It is recommended that authors be more systematic in reporting their results. They need to comment on the limitations of their elasticity estimates since these have repercussions on policy recommendations made based on their results.

What Determines Local Governments' Technical Efficiency? The Case of Road Maintenance

While there are numerous studies on the measurement of the technical or cost efficiency of local governments, the analysis of the main drivers of this efficiency has attracted far less attention in this literature. However, information about the main sources of (in) efficiency are not unimportant, since they can provide useful information for (local) policy-makers. Therefore, the aim of this paper is to add to the existing literature by studying the determinants of local governments' efficiency. For this purpose we focus on one particular area of public goods provision, namely the construction and maintenance of (county) roads, instead of the local government as a whole. This avoids, at least to a certain degree, the problem of defining a comprehensive set of reasonable input and output indicators fully describing local governments' activities, and therefore reduces potential sources of measurement errors. Our empirical analysis is based on a broad panel of German counties rather than a crosssection used in the most previous studies which investigated the determinants of efficiency. The German counties are an interesting case to study, since one of the main tasks of these counties is the construction and maintenance of county roads. In order to determine the main drivers of efficiency in road maintenance, we first calculate efficiency indices using non-parametric (Data Envelopment Analysis) and parametric (stochastic frontier analysis) estimation techniques. In a second step, we examine how these efficiency indices can be explained by a number of exogenous (e.g. socio-economic, fiscal, political) variables. More specifically, we apply and compare four different estimation approaches to detect the potential sources of (in) efficiency. This broad variety of estimation approaches allows us to test and check the robustness of the derived results. The results of our analysis show that (controlling for numerous characteristics of the counties) the disposable income of the counties' citizens, intergovernmental grants for county roads, and the payments to the counties influence technical efficiency negatively. For the political variables we find weak evidence that efficiency decreases with an increasing share of seats of left-wing parties in the county council; on the other hand, the hypothesis that efficiency decreases with the degree of political concentration in the county council could not be confirmed. Moreover, the analysis shows that not all of the four estimation approaches are consistent concerning the sign of the coefficients as well as the (statistical) significance. Therefore, focusing on just one estimation method, as it was done in the most previous studies investigating the determinants of local governments' efficiency, may be deceptive. To test the robustness of the results, different estimation approaches should be applied and compared.

Seepage meter: progressing a simple method of directly measuring water flow between surface water and groundwater systems

Many important water issues such as over-allocation, stream salinity and environmental flows are influenced by the interaction between rivers and underlying aquifers. There are many indirect ways of estimating this flux (such as using hydrographs, tracers or geophysics) but the most common direct method is the use of seepage meters. Over recent decades, various modifications have been made to the basic seepage meter to address potential sources of measurement error and to handle operational issues. These aim to reduce the impact of factors such as upward advection of interstitial water (the Bernoulli effect), venturi effects of stream flow on the collection bag, anomalous short-term influx due to bag properties, gas accumulation in the chamber, frictional resistance causing head losses, ineffective seals and capture of shallow throughflow (rather than groundwater). We have attempted to incorporate these improvements in our seepage meter design and development of simple field procedures, which were trialled in two contrasting catchments (Border Rivers and Lower Richmond) in Australia. The field trials had mixed success, highlighting the potential for spurious seepage flux measurements due to these operational issues.

Characterization of dose-dependent Young's modulus for a radiation-sensitive polymer gel

Radiation-sensitive polymer gels for clinical dosimetry have been intensively investigated with magnetic resonance imaging (MRI) because the transversal magnetic relaxation time is dependent on irradiation dose. MRI is expensive and not easily available in most clinics. For this reason, low-cost, quick and easy-to-use potential alternatives such as optical computed tomography (CT), x-ray CT or ultrasound attenuation CT have also been studied by others. Here, we instead evaluate the dose dependence of the elastic material property, Young's modulus and the dose response of the viscous relaxation of radiation-sensitive gels to discuss their potential for dose imaging. Three batches of a radiation-sensitive polymer gel (MAGIC gel) samples were homogeneously irradiated to doses from 0 Gy to 45.5 Gy. Young's modulus was computed from the measured stress on the sample surface and the strain applied to the sample when compressing it axially, and the viscous relaxation was determined from the stress decay under sustained compression. The viscous relaxation was found not to change significantly with dose. However, Young's modulus was dose dependent; it approximately doubled in the gels between 0 Gy and 20 Gy. By fitting a second-order polynomial to the Young's modulus-versus-dose data, 99.4% of the variance in Young's modulus was shown to be associated with the change in dose. The precision of the gel production, irradiation and Young's modulus measurement combined was found to be 4% at 2 Gy and 3% at 20 Gy. Potential sources of measurement error, such as those associated with the boundary conditions in the compression measurement, inhomogeneous polymerization, temperature (up to 1% error) and the evaporation of water from the sample (up to 1% error), were estimated and discussed. It was concluded that Young's modulus could be used for dose determination. Imaging techniques such as elastography may help to achieve this if they can provide a local measurement of Young's modulus, which may eliminate problems associated with the boundaries (e.g. variation in coefficient of friction) and inhomogeneous polymerization. Elastography combined with a calibration should also be capable of mapping dose in three dimensions.

Ethnic Variability in Retinal Vessel Caliber: A Potential Source of Measurement Error from Ocular Pigmentation?—The Sydney Childhood Eye Study

To describe the effects of ethnicity and iris color on measurement of retinal vascular caliber. The Sydney Childhood Eye Study (SCES) examined 1740 6-year-old children from 34 randomly selected Sydney schools during 2003 and 2004. Retinal arteriolar and venular calibers (central retinal arteriolar [CRAE] and central retinal venular [CRVE] equivalents) were measured from retinal photographs by a standardized computer-assisted Associations of retinal vascular caliber with ethnicity and iris color were analyzed. Of the total participants, 1612 (92.6%) had gradable retinal photographs. CRAE and CRVE were normally distributed, with means (SD) of 163.2 (14.0) and 227.3 (18.3) microm, respectively. Both arteriolar and venular calibers were substantially wider in the East Asian than in the Caucasian children (CRAE, 171.5 mum vs. 160.5 mum; and CRVE, 240.5 microm vs. 222.4 microm; P < 0.0001 for both comparisons). Among the Caucasian children, darker iris color was associated with wider arteriolar and venular caliber: CRAE increased from 157.5 microm in blue eyes to 169.2 microm in dark brown eyes (P for trend < 0.0001), and CRVE increased from 218.4 microm in blue eyes to 230.0 microm in dark brown eyes (P for trend < 0.0001). Among the children with dark brown eyes, there was no significant difference in CRAE between the Caucasian and the East Asian children, although mean CRVE was still approximately 10 mum wider in the East Asian than in the Caucasian children. Retinal vessel caliber was wider in the children of East Asian ethnicity. This difference was explained principally by darker iris color. Retinal pigmentation, as approximated by iris color, could be an important source of error in the measurement of retinal vessel caliber. If confirmed, this may affect comparisons of retinal vessel caliber between subjects with different ethnic backgrounds.