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Results for “measurement error”

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At least 19 recordsLinked to original sources
PubMed1977

The effects of measurement errors on some multivariate procedures.

The effects of random errors of measurement on a variety of basic multivariate procedures are discussed. For some procedures, the effect is one of attenuation (i.e., simply reducing the estimated strength of association). For others, the effect may be to alter the apparent direction of association. Some proposed solutions to the problems caused by errors of measurement are presented, and areas requiring further research are pointed out.

California↗
PubMedDate not supplied

Error measures for objective assessment of scene segmentation algorithms.

Scene segmentation is an important element in pattern recognition problems. Previous efforts to evaluate and compare scene segmentation procedures have been largely subjective. Quantitative error measures would facilitate objective comparison of scene segmentation algorithms. A theoretical discussion leading to a new generalized quantitative error measure, G2, based on comparison of both pixel class proportions and spatial distributions of "true" and test segmentations, is presented. This error measure was tested on 14 manual segmentations and 40 gynecologic cytology specimens segmented with five different scene segmentation techniques. Results indicate that G2 seems to have the desirable properties of correlation with human observation, categorization of error allowing for weighting, invariance with picture size and ease of computation necessary for a useful scene segmentation error measure.

Autoanalysis↗
PubMed1977

The Humphrey Vision Analyzer tm: reliability and validity of refractive-error measures.

Four subjective measures of the refractive error of 42 eyes (21 patients) were obtained by 2 examiners, one using a Humphrey Vision Analyzer TM and the other using a conventional refractor. Each examiner made 2 separate measures of each subject's refractive error, one without and one with an added cylindrical lens chosen at random from a predetermined set of powers and axes. The order of using the instruments and the added lenses was mixed. Measures of the refractive errors differed with the 2 instruments by approximately the same amount on average as did duplicate measures with either instrument. Refractive-error measures obtained with the 2 instruments are about as valid as they are repeatable.

Adult↗
PubMed1978

Statistical analysis of measurement errors of binding data in the Farr technique.

A detailed statistical analysis of measurement errors in the Farr technique is performed, and approximated formulas for the error covariances are given. These formulas are then checked by means of experimental data. In particular, the analysis shows that the usually adopted linear extrapolation for the estimate of total antibody sites concentration may lead to relevant errors in the affinity distribution determination due to the low accuracy of data at high values of free hapten concentration. Conversely, this analysis may constitute the basis for implementing an optimal estimate procedure.

Animals↗
PubMed1977

Measurement errors in pneumotachography due to pressure transducer design.

When pneumotachography is used during intermittent positive pressure ventilation (IPPV), the design of some differential pressure transducers can cause measurement errors. These errors may be avoided by using differential pressure transducers which have small, equal chambers free from temperature sensitive electrical elements. Few of the transducers which are sensitive enough for clinical use fulfil these requirements.

Diagnostic Errors↗
PubMed1976

The effect of measurement error on differences in hospital expenditures.

Differences in expenditures for medical care among various subgroups in the population according to age, income, residence, and ethnicity have important public policy implications. However, few efforts have been made to assess the extent to which these apparent differences among subgroups observed in social surveys may be influenced by measurement error. This paper provides a framework for examining the impact of various kinds of error including random error and biases. The framework is applied to data on hospital expenditures from a national survey of health services expenditure which includes in addition to consumer reports, verifying information from hospitals, physicians, and third-party payers who provided services to persons in the sample. Differential error according to demographic and social characteristics is estimated. The impact of such differential error on conclusions about the distribution of health resources is discussed.

Age Factors↗
PubMed1977

Sheep lactate entry-rate measurements: error due to sampling jugular blood.

Carotid arterial and jugular venous blood samples were taken simultaneously during primed continuous infusions of L-[U-14C]lactate in four sheep. The mean rate (n = 4) of total net formation of lactate (0.394 +/- 0.047 mg C/min per kg) calculated from the results obtained by analyzing the jugular blood samples for lactate concentration and specific radioactivity was significantly higher (0.01 greater than P greater than 0.005) than the mean rate (n = 4) calculated from the results of analysis of the arterial samples (0.302 +/- 0.036 mg C/min per kg). The error in the estimation of the rate of total net formation of lactate due to jugular sampling resulted from the negative arteriovenous difference found for lactate across the tissues of the head. These results illustrate the general need for examination of the suitability of venous sampling in experiments that make use of the continuous infusion isotope-dilution method.

Animals↗
PubMed2026

Test-retest reliability of spatiotemporal, kinematic, and kinetic measures in marker-based 3D gait analysis: A systematic review.

BACKGROUND: Marker-based 3D gait analysis (3DGA) is widely used to quantify impairments and evaluate treatment effects. For longitudinal clinical interpretation, clinicians and researchers need reference values for inter-session measurement error. For this purpose, this systematic review synthesized Standard Error of Measurement (SEM) values for spatiotemporal, kinematic, and kinetic (moments) outcomes obtained from marker-based 3DGA studies. METHODS: PubMed and Scopus were searched (final search: 11 December 2025). Studies reporting inter-session test-retest SEM and/or MDC for steady-state overground or treadmill walking using marker-based motion capture were included. Two authors screened records and appraised methodological/reporting quality using a custom tool informed by COSMIN, GRRAS, and biomechanics-specific items. Due to heterogeneity, results were synthesized descriptively using study-level median SEM values, stratified by joint, plane, population (healthy, pathological, single subgroups), and walking condition. Minimal Detectable Change (MDC) values were computed for all available data. RESULTS: Thirty-four studies (762 participants, 44.2% females) were included, with substantially more evidence for overground than treadmill walking. Overground spatiotemporal outcomes showed low errors (walking speed SEM of 0.06 m/s; timing typically ≤0.03 s; spatial parameters generally ≤0.03 m). For joint kinematics during overground walking, median SEMs were 2.4° (sagittal), 1.9° (frontal), and 3.3° (transverse). The corresponding joint-kinetic SEMs were approximately 0.06, 0.04, and 0.03 Nm/kg, respectively. Treadmill data followed similar patterns. SIGNIFICANCE: Marker-based 3DGA allows for accurate assessment of spatiotemporal, kinematic, and kinetic gait features. We provided detailed SEM/MDC lookup tables to support clinical decision-making. Results further offer a benchmark for validating emerging gait assessment technologies (e.g., markerless systems) against realistic limits of marker-based 3DGA.

Humans↗
PubMed1977

Sources of error in measuring cerebrospinal fluid formation by ventriculocisternal perfusion.

Ventriculocisternal perfusion is regarded as a precise method of measuring the rate of formation of cerebrospinal fluid (CSF) but it possesses inherent potential sources of error. Using the technique to measure CSF formation rate in the rhesus monkey, we have observed rate changes when none were expected. Most puzzling has been the steady decline of CSF formation rate at 4 percent each hour during the final five hours of a seven hour perfusion although variables known to affect CSF formation remained stable. In addition, alterations in rate caused by artefacts were observed in experiments in which craniospinal blood volume was changed by sudden changes of either PCO2 or central venous pressure. Mobilisation or sequestration of incompletely equilibrated CSF is believed responsible. In other experiments, a small increase of intracranial pressure produced by increasing outflow resistance was quickly followed by an apparent reduction of CSF formation. We have concluded that to assess accurately the effect a variable has on the rate of CSF formation, one must control perfusion time and craniospinal blood volume as well as intracranial pressure.

Animals↗