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PubMed2004

A simple error classification system for understanding sources of error in automatic speech recognition and human transcription.

OBJECTIVES: To (1) discover the types of errors most commonly found in clinical notes that are generated either using automatic speech recognition (ASR) or via human transcription and (2) to develop efficient rules for classifying these errors based on the categories found in (1). The purpose of classifying errors into categories is to understand the underlying processes that generate these errors, so that measures can be taken to improve these processes. METHODS: We integrated the Dragon NaturallySpeaking v4.0 speech recognition engine into the Regenstrief Medical Record System. We captured the text output of the speech engine prior to error correction by the speaker. We also acquired a set of human transcribed but uncorrected notes for comparison. We then attempted to error correct these notes based on looking at the context alone. Initially, three domain experts independently examined 104 ASR notes (containing 29,144 words) generated by a single speaker and 44 human transcribed notes (containing 14,199 words) generated by multiple speakers for errors. Collaborative group sessions were subsequently held where error categorizes were determined and rules developed and incrementally refined for systematically examining the notes and classifying errors. RESULTS: We found that the errors could be classified into nine categories: (1) announciation errors occurring due to speaker mispronounciation, (2) dictionary errors resulting from missing terms, (3) suffix errors caused by misrecognition of appropriate tenses of a word, (4) added words, (5) deleted words, (6) homonym errors resulting from substitution of a phonetically identical word, (7) spelling errors, (8) nonsense errors, words/phrases whose meaning could not be appreciated by examining just the context, and (9) critical errors, words/phrases where a reader of a note could potentially misunderstand the concept that was related by the speaker. CONCLUSIONS: A simple method is presented for examining errors in transcribed documents and classifying these errors into meaningful and useful categories. Such a classification can potentially help pinpoint sources of such errors so that measures (such as better training of the speaker and improved dictionary and language modeling) can be taken to optimize the error rates.

Automation↗
PubMed1987

Sources of error in registering suicide.

Sources of error theoretically possible in the registration of suicide are discussed. Using cause-of-death statistics for each of the Nordic countries, the relative influence of the various sources of error is evaluated. Two types of sources of error are identified, one is when cause-of-death is registered as drowning and the other is when it is registered as "unknown". Results have shown however, that the low probability of suicide in these cases, and consequently small numbers involved, could hardly influence differences in rates between the Nordic countries. The differences found in suicide statistics therefore reflect true differences in the frequency of suicide between these countries.

Accidents↗
PubMed2004

An event-related potential study of two kinds of source judgment errors.

The neural correlates of source judgment errors for confusable and nonconfusable source-item pairings were investigated. At study, subjects were presented with a series of lists of word pairs. Word pairs belonging to the same list were formed by pairing one of two associated words with different associates of an unstudied theme word (e.g., ship-frost, captain-chilly, ship-freeze, captain-frigid, etc., in one list; wife-pane, husband-glass, wife-curtain, husband-sill, etc., in another list). At test, subjects discriminated 'Old pairs' (e.g., ship-frost) from 'Intra' rearranged pairs (e.g., ship-chilly), 'Inter' rearranged pairs (e.g., ship-pane), and 'Old-New' pairs (e.g., ship-bulb). Event-related potentials (ERPs) were recorded for each class of test item. Similar proportions of 'yes' responses to Old and Intra rearranged pairs were observed, but the false alarm rate for Inter rearranged pairs was markedly lower. ERPs elicited by correctly classified Old pairs and false alarms to Intra rearranged pairs were indistinguishable and exhibited 'left parietal' and 'right frontal' effects, characteristic of recollection-based recognition. ERPs for false alarms to Inter rearranged pairs did not show these effects. It is concluded that source judgment errors for confusable source-item pairings are mediated by the same processes that support correct source judgments. Such errors reflect recollection of gist information which is nondiagnostic with respect to source.

Analysis of Variance↗
PubMed1979

Ultrastructure of skin biopsy specimens in lysosomal storage diseases: common sources of error in diagnosis.

Common sources of error in the diagnosis of lysosomal storage diseases by ultrastructural examination of skin specimens have been identified in a series of biopsies from 72 patients. Four principal factors have emerged as leading pitfalls and sources of error in diagnosis. First, the skin biopsy technique itself may lead to alterations of normal skin ultrastructure. Second, artifacts may be produced during fixation and preparation of tissue for electron microscopy. Third, cellular organelles and structures normally present in human skin may be mistakenly interpreted as pathological. Fourth, the use of cultured skin fibroblasts for ultrastructural identification of storage material is often accompanied by artifacts induced in tissue culture and is not recommended. Recognition of these common problems may aid interpretation of the fine structure of skin abnormalities. Furthermore, when skin biopsy specimens are used as the primary source of diagnostic material, correlation of both skin ultrastructure and assay for specific lysosomal enzymes in cultured dermal fibroblasts will facilitate diagnostic accuracy.

Biopsy↗
PubMed1976

Bone density measured by photon scattering. II. Inherent sources of error.

The origins of inherent sources of error in results of measurements of bone density by a photon scattering technique are described and their effects are predicted theoretically. The predictions are confirmed experimentally. The prime source of error is multiple scattering. A procedure has been developed to correct the observed densities for effects of multiple scattering.

Bone Diseases↗
PubMed1997

Clinical and neurocognitive aspects of source monitoring errors in schizophrenia.

OBJECTIVE: Source monitoring, an aspect of memory that involves judgments about the origin of information, has been found to be more prone to errors in schizophrenic subjects than in normal persons. To examine the precise nature of such errors and their relationship to clinical and neurocognitive variables, the authors compared schizophrenic and normal subjects. METHOD: Schizophrenic subjects who had been medication free for 1 week (N = 26) and demographically matched normal subjects (N = 21) performed a source monitoring task and were assessed on current psychiatric symptoms, IQ, and frontal lobe functioning. RESULTS: The schizophrenic subjects had normal recognition memory of target words (recognition hits) and a normal generation effect but made more errors than the comparison subjects in identifying the source of target words. Specifically, the schizophrenic subjects made more errors in remembering the source of new and self-generated items, and they tended to attribute items to an external source. In 11 retested subjects, these errors were stable and independent from medication status after a 2-year interval. Secondary analyses suggested that certain source monitoring errors may be associated with hostility and lower IQ. When the effect of IQ was controlled, correlations with frontal dysfunction were not significant. CONCLUSIONS: Schizophrenic subjects make significantly more source monitoring errors than normal subjects, but not because of problems with recognition memory hits or with the generation effect. This tendency may be trait like and may be related to hostility. Lower IQ in schizophrenia plays a partial role in these errors, but frontal dysfunction does not.

Adult↗
PubMed1988

Interobserver variability. A source of error in obstetric ultrasound.

Several sources of error encountered in obstetrical ultrasound examination have been analyzed from a computerized ultrasound database. The variability in measuring fetal landmarks and visualization of fetal structures were found to be significantly different among three registered sonographers who examined 1,410 consecutive second and third trimester patients. The rate of successful measurement of biparietal diameter (BPD) and average abdominal diameter (AAD), as well as successful visualization of fetal stomach and/or kidneys were statistically different among the three sonographers. Only the fetal femur length was consistently measured by all three sonographers. The bias in terms of actual millimeters measured was significantly different for both BPD and AAD. The bias related to the BPD was in the magnitude of 1 mm, while the bias related to the AAD was almost 3 mm. The clinical significance of these findings and the value of the computer to perform periodic checks to assure quality control in a busy ultrasound service are discussed.

Diagnostic Errors↗
PubMedDate not supplied

Measurement error in functional balance and mobility tests for people with stroke: what are the sources of error and what is the best way to minimize error?

OBJECTIVE: To assess the degree and source of measurement error in functional balance and mobility tests for people with stroke, and to identify the most effective method of data collection to minimize error. DESIGN: To assess the degree and source of error, the total, systematic, and random error were calculated for within-session, test-retest, and interrater testing. To identify the most effective method of data collection, the total error was calculated for 4 data collection methods: 1 familiarization trial, then scoring a 2nd trial; 2 familiarization trials, then scoring a 3rd trial; averaging 2 trials, then averaging 3 trials. SETTING: Stroke services in National Health Service hospitals. PATIENTS: Thirty-five people with a poststroke hemiplegia. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Five tests provided interval-level data: arm raise (sitting and standing), weight shift, tap, and step-up. Four tests provided ratio-level data: forward reach (sitting and standing) and 5-m timed walk (with and without an aid). RESULTS: Total measurement error ranged from zero for the step-up test to 55% for within-session error for the 5-m walk without an aid. Ratio data tests showed somewhat greater error than interval data tests (5%-55% vs. 0%-46%). A within-session practice effect for the standing forward reach, 5-m walk (with and without an aid), and weight shift tests was found. For the other tests, random error was greater than the systematic error. Interrater testing had the least error. For most tests, the average of 2 trials produced the least measurement error. For the 5-m walk, the mean obtained from 2 or 3 trials was equally effective. For the step-up test, the mean of 3 trials was slightly more effective. The overall error from all 3 sources was 3 lifts for sitting arm raise, 11 cm for sitting forward reach, 3 lifts for the standing arm raise, 7.5 cm for standing forward reach, 4.5 s for walking with an aid, 3 shifts on the weight shift test, 1.1 s for walking without an aid, 2 taps, and 1 step up. CONCLUSION: The tests using interval data showed less error than ratio-data tests and may be preferable measurement tools. Taking an average of 2 trials was the most accurate data collection method.

Aged↗
PubMed1990

Optimal interelectrode distance with the method of source density analysis.

Three error sources which contribute to the total error of the second space derivative (SSD) used with the method of current source density analysis (CSD) were examined. The approximate formula usually used with CSD was the first error source. Another error originated from the finite interelectrode distance. The measurement error of the device with which the potential was recorded was the third error source herein considered. A relative SSD error was determined to estimate the effect of the errors examined. The experimental data (a section from the three-dimensional potential profile in annuran cerebellum produced by parallel fiber activation) were fitted by polynomials, Fourier expansion and cubic splines. Then a preferable interelectrode distance was obtained corresponding to the minimal relative error.

Animals↗
PubMed1989

[Sources of error in automated static perimetry].

Several sources of errors in interpreting computerized visual fields (learning effect, miotic pupil, sub-optimal refraction, dirty contact lenses, inadequate patient cooperation, anatomical obstacle, and choice of the wrong program) are described with the help of examples. Their identification should result in more reliable diagnoses.

Contact Lenses↗
PubMed1997

Spinal range of motion. Accuracy and sources of error with inclinometric measurement.

STUDY DESIGN: A quantitative construct assessing accuracy and component analysis of sources of error rather than reliability coefficients was tested prospectively in human performance measurements of lumbar spine motion using a cohort of healthy individuals. OBJECTIVES: To evaluate the accuracy of lumbar spine sagittal motion measurements using a computerized inclinometer, which involved progressive analysis of sources of error to identify the most problematic sub-components of the measurement process and device. SUMMARY OF BACKGROUND DATA: Many previous studies have described the reliability of inclinometric lumbar motion measurement techniques, but with inconsistent analysis about sources of error to explain identified variability. Similar deficiencies exist in identifying sources of error leading to variability for other human performance measurements (e.g., strength, endurance. lifting capacity, etc.). Yet, range of motion has important clinical applications in monitoring progress and assessing temporary and/or permanent impairment. This makes it especially important for clinicians to be able to recognize and correct factors that limit accurate measurements affecting clinical utility. METHODS: A computerized inclinometer was used for measuring the sagittal lumbar mobility of 38 healthy individuals after bench testing the device itself for device error. The human performance test conditions were: 1) initial test on study participants by untrained test administrators with no control of human performance or procedural variables, 2) identical tests by procedurally trained test administrators controlling human performance variability by monitoring and controlling total motion, and 3) test by procedurally trained test administrators without controlling for human performance variability. RESULTS: The accuracy of the methodology progressively was degraded by the various sources of error. Device error was negligible relative to error associated with the test process itself. Lack of test administrator training and the magnitude of the measured quantity were the major factors in test degradation. Combined (gross) lumbar flexion was the most accurate measure (worst case > 95% accuracy for overall test conditions), whereas pelvic extension was the least accurate (worst case > 36%). CONCLUSIONS: Clinical utility of lumbar spine sagittal motion measurement is highly sensitive to test administrator training to bridge pitfalls to measurement accuracy (bony landmarks, "rocking" of inclinometer on sacrum, etc.). Magnitude of the measurement is another important accuracy factor because absolute error tends to remain relatively constant. Device accuracy is usually an insignificant component of overall test accuracy. Analysis of human performance measurements, such as spinal range of motion, may be facilitated by physics-based assessment of accuracy and procedural error in providing more sophisticated analysis than is customarily accessible through reliability coefficients. Previous studies often failed to recognize correctable procedural errors, rarely addressed them, and almost never quantitated them.

Adult↗
PubMed2001

Remembering the color of objects: an ERP investigation of source memory.

Subjects studied pictures of common objects outlined in either red or green and were asked to memorize the objects and their associated colors. Event-related potentials (ERPs) were recorded during subsequent inclusion (i.e. item) and exclusion (i.e. source) memory tasks. The main goal of the experiment was to determine if brain signatures for familiarity and recollection, two behavioral processes thought to account for episodic memory performance, would be observed in the pattern of ERP results. For correctly recognized items, early, posterior old/new effects were recorded (approximately 300--600 ms) that did not differ in magnitude or scalp distribution between item and source memory tasks. A subsequent long-duration occipitally focused negativity (approximately 800 ms peak) was evident in the source but not the item memory task. The ERPs associated with 'source errors' in the source memory task also showed robust early old/new effects. However, 'source error' ERPs lacked frontal scalp activity compared to those associated with correct source attribution. The data suggest that a recollective response may require frontal involvement whereas a decision based on familiarity may not.

Adult↗
PubMed1997

Source placement error for permanent implant of the prostate.

The performance of ultrasound (US) and fluoroscopic-guided permanent 125I source implant of the prostate using CT identification of the source positions has been evaluated. Marker seeds were implanted during the planning study to assist in the alignment of the US and CT prostate volumes for treatment planning and to guide the placement of needles. The relative positions of the needles and marker seeds were checked by fluoroscopy. A postimplant CT study was used to input the radioactive source positions and to register the sources relative to the preimplant CT and US prostate volumes and the planned source distribution. Source placement errors observed were categorized as: (1) source-to-source spacing differences; (2) needle placement error, both depth and position; and (3) seed splaying, particularly near the prostate periphery. Errors due to source splaying and spacing were in part attributed to prostate motion. Later refinements included fixed-spaced string sources, for which placement errors were smaller than for unattached sources. However, source placement errors due to needle placement error and prostate motion remained unchanged.

Brachytherapy↗
PubMed2002

Setting performance goals and evaluating total analytical error for diagnostic assays.

BACKGROUND: Total analytical error has been a useful metric both to assess laboratory assay quality and to set goals. It is often estimated by combining imprecision (SD) and average bias in the equation: total analytical error = bias + 1.65 x imprecision. This indirect estimation model (referred to as the simple combination model) leads to different estimates of total analytical error than that of a direct estimation method (referred to as the distribution-of-differences method) or of simulation. METHODS: A review of the literature was undertaken to reconcile the different estimation approaches. RESULTS: The simple combination model can underestimate total analytical error by neglecting random interference bias and by not properly treating other error sources such as linear drift and outliers. A simulation method to estimate total analytical error is outlined, based on the estimation and combination of total analytical error source distributions. Goals for each total analytical error source can be established by allocation of the total analytical error goal. Typically, the allocation is cost-based and uses the probability of combinations of error sources. The distribution-of-differences method, simple combination model, and simulation method to evaluate total analytical error are compared. Outlier results can profoundly influence quality, but their rates are seldom reported. CONCLUSIONS: Total analytical error should be estimated either directly by the distribution-of-differences method or by simulation. A systems engineering approach that uses allocation of the total analytical error goal into error source goals provides a cost-effective approach to meeting total analytical error. Because outliers can cause serious laboratory error, the inclusion of outlier rate estimates from large studies (e.g., those conducted by manufacturers) would be helpful in assessing assay quality.

Clinical Laboratory Techniques↗
PubMed1989

Identification of the major sources of error in estrogen receptor measurements for individual laboratories using both tissue and cytosol samples.

The major sources of error between laboratories performing estrogen receptor measurements in tissue samples were identified for 17 participating laboratories in a trial conducted by the Australasian Quality Assurance programme. Both tissue and cytosol samples were provided, and the In-House assays were compared with the ER-EIA kit (Abbott Laboratories, U.S.A.) as a reference assay. For both the In-House and Abbott assays, tissue samples resulted in a between laboratory CV of about 55% and a within laboratory CV of about 30%. In contrast to tissue samples, the between laboratory CV for cytosol samples was reduced to 41% for the In-House assays and to 33% for the Abbott assay, whereas the within laboratory CV was reduced to 10% for both types of assay. The different methods of tissue homogenization by themselves were not found to be sources of error, and protein extraction efficiency from tissue was strongly correlated with protein measurement (P less than 0.0005). The major sources of error due to protein measurement, cytosol preparation, In-House and Abbott assays were evaluated for individual laboratories. The results indicated absence of any major sources of error for four laboratories, while one, two and three or more sources were indicated for seven, three and three laboratories respectively. The conclusion that about half the participants need to improve their ER assays was confirmed by three independent reviews. Furthermore, the trial demonstrated that tissue samples are essential as quality assurance material for a realistic assessment of ER assays in biopsy specimens.

Animals↗
PubMed1993

Sources of error in use of beta-2 transferrin analysis for diagnosing perilymphatic and cerebral spinal fluid leaks.

Beta-2 transferrin is a protein found in cerebral spinal fluid and inner ear perilymph, but not in blood, nasal, or ear secretions. The clinical use of this test has been previously demonstrated, but sources of test error have not been addressed. The purpose of this study was to evaluate sources of error related to this test in order to improve its clinical use. We reviewed the specimens submitted for beta-2 analysis over the first 12 months of test availability at our institution to identify potential factors leading to test error. Sources of error were categorized into the following groups: sample collection, delivery, and extraction factors; assay factors; physician-related factors; and patient-related factors. The test for beta-2 transferrin is a valuable diagnostic tool for the management of difficult clinical problems, provided the physician is aware of potential factors that can lead to test error and clinical mismanagement.

Bias↗
PubMed1977

The measurement of distortion: theoretical considerations.

When very find measurements are recorded for the purpose of establishing distortion values, from the standpoint of accuracy, specific procedures must be developed. In the procedural system defined here, a potential major source of error is indicated and the means of overcoming this error established. From the standpoint of modern electronic technology, the use of an analogue-to-digital interface with a digital computer is considered extremely advantageous and allows the utilization of technical help to carry out the preliminary measurements. Under these circumstances, major error sources, such as reader error and calculation error, are eliminated. Further, multiple readings on each point can be made without significant sacrifice of time. This latter statement can help define the reading accuracy on each point and allows an immediate further set of readings on any point that has a large variation in the initially established set of readings. The applicability of this approach to any system in which an accurate set of readings is required to define distortion or some other parameter is limited only by the imagination of the investigator. Measuring points can be established at any desired location, and the number required is a function of the mathematical analysis being attempted. The use of a digital computer to compute the final values allows an immediate remeasurement of the initial values if necessary, since the computer response time is of the order of seconds for the calculations carried out. This is very important if changes in the experimental setup are likely to occur with time. In general, a computerized scheme such as is proposed here allows the investigator to concentrate on the experiment rather than the calculation of results. Also, the use of technical help to carry out delicate measuring procedures can allow the investigator more time to analyze the final results.

Analog-Digital Conversion↗