Sources Of Error In Determination Research Articles

Data electronically extracted from the electronic health record require validation.

Determine sources of error in electronically extracted data from electronic health records. Categorical and continuous variables related to early-onset neonatal hypoglycemia were preselected and electronically extracted from records of 100 randomly selected neonates within 3479 births with laboratory-proven early-onset hypoglycemia. Extraction language was written by an information technologist and data validated by blinded manual chart review. Kappa coefficient assessed categorical variables and percent validity continuous variables. 8/23 (35%) categorical variables had acceptable Κappa (1-0.81); 5/23 (22%) had fair-slight agreement, Κappa < 0.40. Notably, "hypoglycemia" had poor agreement, Κappa 0.16. In contrast, 6/8 continuous variables had validity ≥ 94%. After correcting extraction language, 6/9 variables were corrected and inter-rater validation improved. However, "hypoglycemia" was not corrected, remaining an issue. Data extraction without validation procedures, especially categorical variables using International Classification of Diseases-9 (ICD-9) codes, often results in incorrect data identification. Electronically extracted data must incorporate built-in validating processes.

Changing Consumer Behavior and Influencing the Food Environment

SUMMARY Promoting consumption of healthier grain-based foods is clearly an important challenge for public health and industry alike. In practice, however, public health and marketing initiatives are frequently characterized by dependence on superficially plausible but unsound research data and naive assumptions about human behavior. As a result, many initiatives are compromised from the outset and wasteful if not in fact counterproductive. These limitations are avoidable. There exists a substantial body of knowledge on human decision making that is fundamentally at odds with common sense and conventional wisdom, and emerging insights from health psychology through to neurobiology offer important insights into just why behavior can be so resistant to change. Against this backdrop, some common sources of error in determinations on human behavior are identified, and data are presented to illustrate how seemingly plausible assumptions can lead to serious strategic miscalculations. Finally, a framework is proposed to guide research and strategic decisions in respect of consumer behavior, including the promotion of grain-based products and innovations.

Ionospheric and hardware fluctuations of the optical path during radio occultation sounding of the earth’s atmosphere in the COSMIC experiment

Ionospheric and hardware fluctuations of optical paths are the most significant sources of errors in determination of the parameters of the neutral atmosphere using the radio occultation method at altitudes above 8 km. The paper presents a spectral analysis of the fluctuations in the optical path during radio occultation measurements in two channels of the GPS system for the perigee altitudes of probing beams in the range from 80 to 100 km, where the contribution of the neutral atmosphere is negligibly small. For analysis, a data set of 300 measurements made during the COSMIC experiment was used. The spectral analysis revealed the maximum cross-correlation of the fluctuations in two channels at a spatial frequency of 2.5 rad/km. Weaker correlation for lower spatial frequencies is determined by hardware noise. Weaker correlation for higher spatial frequencies is determined by the effects of diffraction by small-scale ionospheric irregularities.

Computational analyses of CO‐rebreathing methods for estimating haemoglobin mass in humans

Measurement of haemoglobin mass (M(Hb)) is used to quantify alterations in oxygen delivery during exercise training or acclimatization to altitude. Uptake of carbon monoxide by haemoglobin is the basis of the common non-radioactive methods to determine M(Hb) in humans. This study used a validated mathematical model to simulate CO uptake during rebreathing protocols and to determine sources of errors in estimation of M(Hb). Our previously published model was validated using experimentally measured carboxyhaemoglobin levels (%HbCO) from arterial, capillary and venous blood sites of human subjects during CO-rebreathing protocols. This model was then used to simulate various CO-rebreathing protocols in 24 human subjects with known M(Hb). Using variables generated by the model, M(Hb) was estimated on the basis of assumptions typically made for calculating the volume of CO bound to myoglobin, the volume of CO exhaled and the volume of CO in the rebreathing system. It was found that inaccurate estimation of the volume of CO bound to myoglobin was the major source of error in determination of M(Hb). Additionally, the size of the error was found to depend on the site of blood sampling because of differences in %HbCO. Regression equations were developed to improve the estimation of volume of CO bound to myoglobin, and a new protocol that is less dependent on the site of blood sampling is proposed.

Two sources of error in determination of the particle concentration reduction factor of the volatile particle remover used in legislated vehicle emission measurement

We investigated sources of error in determination of the particle concentration reduction factor (fr) of the volatile particle remover (VPR) used in legislated vehicle emission measurement. Sodium chloride and soot are two of the most frequently used materials of particles used in the fr evaluation. We identified two sources of error that are associated with the use of these materials: one is the variation of the detection efficiency of condensation particle counters (CPCs) against sodium chloride particles, which was found to depend on the preheated temperature of the particles and the other is the size shrinkage of soot particles generated with a propane flame burner that are not thermally pre-treated, when the particles were heated at temperatures typically set at the evaporation tube of VPRs. These two sources of error have presumably caused disagreement of fr values obtained with particles of the two materials. We found that, by selecting appropriate CPCs and also by sufficiently pre-heating the particles, disagreement due to these errors could be eliminated. As a result, consistent fr values were obtained between measurements with the two different particle materials, i.e. sodium chloride and soot.

Causes and consequences of errors in determining sorption capacity of coals for carbon dioxide at high pressure

Abstract Recent comparisons of CO2 sorption by coals at high pressures have shown major differences between the results obtained by different laboratories. These need to be resolved for laboratory estimation of CO2 sequestration in coal seams to be useful. A compilation of potential sources of error in determination of sorption characteristics and their impact on sorption measurements is provided here. A series of tests is also provided that can be used to identify and reduce such errors in measurement. For example, an error in temperature produces a characteristic distortion of the sorption curve for carbon dioxide, which can be corrected to some extent. A negative value for excess sorption at high pressure is almost certainly diagnostic of either a cell volume that has been overestimated or that some part of the substrate that is inaccessible to the gas is accessible to helium. The major source of variation between results from the different laboratories that supplied the closest sorption values was found to be variations in the assumed free space volume, which could be due to discrepancies in determined helium density or measured cell volume. Including a term in the sorption model that is proportional to gas density will markedly reduce the influence of such errors in estimating sorption capacity or heats of sorption. The influence of swelling and moisture on sorption isotherms is also quantified here. Correction for swelling of coals in carbon dioxide changes the estimated sorption capacity by less than 1%, if a term that is proportional to gas density is included as a free parameter in the model fitting the isotherm.

SU‐FF‐T‐311: LINAC Dosimetry: Benchmark Data Set Uncertainty

Purpose: Determine sources of error in the collection of a Benchmark Data set for LINAC dosimetry and provide methods of error correction that will ensure the highest possible accuracy of the dosimetric data. Method and Materials: Guided by the measurement requirements for the Benchmark Datasets, the sources of experimental error can be divided into 3 sources: 1) discretization and volume averaging errors; 2) Stochastic errors; and 3) Systematic or artifactual errors. Measurements will be made in a 3D water phantom scanning system and in a water‐equivalent solid phantom that will allow the insertion of heterogeneous components. Results: We present theoretical analyses of the expected errors associated with ion chamber, radiochromic film, and diode measurements and provide specific techniques that will enable high spatial resolution of dose gradients resulting from beam limiters and dose perturbations in and around heterogeneity interfaces, such as air/tissue, lung/tissue, bone/tissue. These techniques include de‐convolution of chamber response and a 3D correction matrix of a film scanner. Conclusion: Theoretical limits of spatial resolution in LINAC dosimetry are achievable and demonstrable using dosimetric tools available today. These tools and methods will be used to collect accurate Benchmark Dosimetry data for future research in Monte Carlo techniques for treatment planning as well as automated software tools that will enable systematic QA of modern treatment planning systems. Conflict of Interest: This project has been funded in part with Federal funds from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services, under Contract No, HHSN261200522014C, NCI grants R01‐CA‐100636, and by Sun Nuclear Corporation.

Bewertung von Spannungszuständen bei der experimentellen Bestimmung des Schubmoduls an zellularen Materialien

The experimental determination of the shear modulus of materials proves to be problematic in practice. The different methods do not only preduce the desired pure shear stress state. In this paper, starting from several experimental implementations of the shear test, possible sources of errors in determination of the shear modulus are discussed. An estimation of the possible error is calculated by numerical simulations. Two examples from the field of cellular metals are given to illustrate the effect of just an approximate realization of the pure shear stress state.

Error sources and error estimates in flow-injection determination of oxidizing and reducing agents

We have determined the sources of the greatest error in determination of oxidizing and reducing agents in a flow-injection approach using a platinum electrode. We have numerically estimated each of the error components.

From image processing to classification: I. Modeling disturbances of isoelectric focusing patterns

In order to optimize the conditions for evaluation of isoelectric focusing (IEF) patterns by digital image processing, the sources of error in determination of the pI values were analyzed together with the influence of a varying background. The effects of band distortions, in the spectra of the individual lanes, were examined. In order to minimize the effect of these distortions, optimal conditions for handling IEF patterns by digital image processing were elucidated. The systematic part of the global deformation on the gels was investigated and an algorithm was developed by which it was possible to correct for a part of the individual distortions. The effects of various corrections for lane distortions were illustrated by classification, using different types of discriminant analysis. Finally the background disturbances were examined, and described by a mathematical model.

Potential sources of error in determination of metabolite ratios in human heart with 31P NMR spectroscopy

Potential sources of error in determination of metabolite ratios in human heart with 31P NMR spectroscopy

ASSESSMENT OF ERRORS ASSOCIATED WITH PLOT SIZE AND LATERAL MOVEMENT OF NITROGEN-15 WHEN STUDYING FERTILIZER RECOVERY UNDER FIELD CONDITIONS1

The high cost of /sup 15/N-labeled fertilizers encourages the use of field plots having minimum size. If plot size is reduced too much, however, lateral movement of N near the plots by mass flow or diffusion within the soil or by translocation through plant roots can become a significant source of error in determinations of fertilizer N recovery. This study was initiated to assess the importance of lateral movement of labeled fertilizer when unconfined plots are used to determine recovery of fertilizer. Corn grain samples were collected at various positions inside and outside /sup 15/N plots, and the /sup 15/N contents of these samples were determined. The data were fit to mathematical models to estimate the extent to which lateral movement of fertilizer N caused errors in determined values of fertilizer recovery for the first, second, and third crops following fertilization. These models also were used to predict the plot size needed for similar /sup 15/N-tracer studies in the future. The results of these studies indicate that /sup 15/N plots having a size of 2 by 2 m are sufficiently large for determining recovery of fertilizer N for corn crops under most conditions. Where lateral movement of fertilizer N inmore » soils is suspected to be a problem, we recommend collection of a few plant samples outside the /sup 15/N plots as insurance against misleading conclusions concerning fertilizer N recovery.« less

Sources of error in determinations of carnitine and acylcarnitine in plasma.

Radioactive and nonradioactive L-carnitine and acyl-L-carnitine were used to evaluate the washing procedures used during the determination of free, total, short-chain, and long-chain acylcarnitine in human and sheep plasma. The volume of fluid trapped by the protein precipitated by perchloric acid is approximately 24% of the total fluid volume and thus contains 24% of free carnitine and short-chain acylcarnitine. Washing twice with distilled water removes about 25% of the long-chain acylcarnitine along with the trapped free carnitine and short-chain acylcarnitines. Washing the pellet twice with a 60 g/L solution of perchloric acid completely removes the trapped free carnitine and short-chain acylcarnitine but does not remove the bound long-chain acylcarnitines. Thus washing with perchloric acid is essential for accurate measurement of long-chain acylcarnitines in plasma samples.

A source of error in determination of blood gases.

A source of error in determination of blood gases.

Source of error in determination of erythrocyte folate by competitive binding radioassay - comments.

Source of error in determination of erythrocyte folate by competitive binding radioassay - comments.

Source of error in determination of erythrocyte folate by competitive binding radioassay - comments.

Source of error in determination of erythrocyte folate by competitive binding radioassay - comments.

Inadequate sample-preparation technique as a source of error in determination of erythrocyte folate by competitive binding radioassay.

Inadequate sample-preparation technique as a source of error in determination of erythrocyte folate by competitive binding radioassay.

Sources of error in determination of available lysine in cottonseed and peanut meals.

AbstractExperiments were made to identify the sources of error in the Rao procedure for available lysine in cottonseed and peanut meals and to estimate the magnitude of each. The partition of squares in analyses of variance of the data reported revealed that the major error can be attributed to sampling. The variances due to other possible sources of error, such as dinitrophenylation, hydrolysis, chromatography, etc., were not significantly different from the error variance, which (after the sampling error is accounted for) corresponds to confidence limits at the 5% level of probability of ±0.5% of the mean of the available lysine concentration.

Instrumental and Procedural Sources of Error in Determination of Bile Pigments in Amniotic Fluid

Abstract Although the Liley spectrophotometric estimation of bile pigments in amniotic fluid [Amer. J. Obstet. Gynecol. 82, 1359 ( 1961)] is widely used, the levels of accuracy and precision necessary for clinically meaningful results have not been clarified. This paper delineates some of the important instrumental and procedural sources of error, and how each affects the final value of ΔA455: (a) A limit of error propagation is presented to show that the uncertainty in ΔA455 due to instrumental factors is considerably larger than is commonly appreciated. (b) It is desirable to use a logarithmic baseline estimation, as did Liley, instead of a linear estimation, which can introduce a serious bias. (c) Failure to establish a true zero-absorbance baseline before scanning the specimen can also result in a significant bias in the calculated ΔA455.

Possible Sources of Large Error in Determinations of Ion–Molecule Reaction Rates with Drift Tube–Mass Spectrometers

Drift tube–mass spectrometers are now used extensively to measure the rate coefficients of ion–molecule reactions. The accuracy which can be obtained in favorable cases is about 10%, but if careful attention is not paid to a number of factors, very large errors can result. The purpose of this paper is to call attention to this fact, which seems not to be widely known, and to enumerate the factors which can lead to these large errors.