High Measurement Error Research Articles

Establishing the Reliability of the GaitON® Motion Analysis System: A Foundational Study for Gait and Posture Analysis in a Healthy Population.

Gait and posture analysis plays a crucial role in understanding human movement, with significant applications in rehabilitation, sports science, and clinical settings. The GaitON® system, a 2D motion analysis tool, provides an accessible and cost-effective method for assessing gait and posture. However, its reliability in clinical practice, particularly for intra-rater consistency, remains to be evaluated. This study aims to assess the intra-rater reliability of the GaitON® system in a healthy population, focusing on gait and posture parameters. A total of 20 healthy participants (10 males and 10 females) aged 18 to 50 years were recruited for the study. Each participant underwent gait and posture assessments using the GaitON® system on two separate occasions, spaced one week apart. Video recordings from anterior and posterior views were used to analyze gait, while images from anterior, posterior, and lateral views were captured to assess posture with markers placed on key anatomical landmarks. The reliability of the measurements was analyzed using intraclass correlation coefficients (ICC), a standard error of measurement (SEM), and the smallest detectable difference (SDD) method. The GaitON® system demonstrated excellent intra-rater reliability across a wide range of gait and posture parameters. ICC values for gait parameters, including hip, knee, and ankle joint angles, ranged from 0.90 to 0.979, indicating strong consistency in repeated measurements. Similarly, ICC values for posture parameters, such as the head alignment, shoulder position, and ASIS alignment, were above 0.90, reflecting excellent reliability. SEM values were low across all parameters, with the smallest SEM recorded for the hip joint angle (0.37°), and SDD values further confirmed the precision of the system. The GaitON® system provides reliable and consistent measurements for both gait and posture analysis in healthy individuals. Its high intra-rater reliability and low measurement error make it a promising tool for clinical and sports applications. Further research is needed to validate its use in clinical populations and compare its performance to more complex 3D motion analysis systems.

Effects of multiple reflections on nonlinear absorption measurements.

Accurate measurement of nonlinear absorption coefficients by transmission-based techniques, such as Z-scan and its modifications, remains challenging due to high measurement errors. In this Letter, we claim that one of the reasons for that could lie in ignoring multiple reflections of light in plane-parallel samples in the presence of multi-photon excitation. Closed-form formulations for transmittance and reflectance coefficients, considering both linear and multiphoton absorption, are obtained in the geometrical optics approximation. The contributions of multiple reflections to the total transmittance are calculated for several II-VI materials reported in the literature. The results show a nonlinear dependence on incident intensity, ranging from 15.7% down to 7.9% for CdS, from 10.3% down to 5.8% for CdSe, and from 18.1% down to 9.1% for ZnSe. The dependence of the contribution of multiple reflections on the sample thickness is shown to exhibit a near exponential decay.

Two-Dimensional Inverse Method to Estimate the Heat Flux Function in a Phase Change Material Heat-Exchanger

A two-dimensional inverse method is presented for estimating the boundary heat flux imposed on phase change materials in the melting/solidification process. The inverse problem is handled by the conjugate gradient method with the adjoint problem for function estimation. The method is verified using unsynthetic data, and the effect of the number of sensors, sensor placement, and measurement errors on the accuracy is investigated. In all cases, it is found that the method remains stable and accurate with a root mean square relative error less than 10%. Also, the number of sensors depends on the desired accuracy, computing time, and frequency of spatial changes in heat flux. Using field measurement is the best option for high accuracy and time-efficient estimation of spatial changes in the heat flux function. The accuracy of the estimated heat flux strongly depends on the sensor distance from the boundary. Therefore, it is desirable to place the sensor as close to the boundary as possible. With the addition of measurement errors, the presented method remains stable even with high measurement errors. This shows that this method can be used for real conditions.

Can isometric testing substitute for the one repetition maximum squat test?

When measuring maximum strength, a high accuracy and precision is required to monitor the training adaptations. Based on available reliability parameters, the literature suggests the replacement of the one repetition maximum (1RM) by isometric testing to save testing time. However, from a statistical point of view, correlation coefficients do not provide the required information when aiming to replace one test by another. Therefore, the literature suggests the inclusion of the mean absolute error (MAE), the mean absolute percentage error (MAPE) for agreement analysis. Consequently, to check the replaceability of 1RM testing methods, the current study examined the agreement of isometric and dynamic testing methods in the squat and the isometric mid-thigh pull. While in accordance with the literature, correlations were classified high r = 0.638-0.828 and ICC = 0.630-0.828, the agreement analysis provided MAEs of 175.75-444.17 N and MAPEs of 16.16-57.71% indicating an intolerable high measurement error between isometric and dynamic testing conditions in the squat and isometric mid-thigh pull. In contrast to previous studies, using MAE, MAPE supplemented by CCC and BA analysis highlights the poor agreement between the included strength tests. The recommendation to replace 1RM testing with isometric testing routines in the squat does not provide suitable concordance and is not recommended.

Measurement properties and normative data of a set of six physical assessments for use in primary healthcare

Purpose To address the high rates of sickness absence due to musculoskeletal (MSK) disorders in Western countries, this study assessed the measurement properties of six standardised physical assessments to aid in treatment planning and provide guidance in work participation decisions. Materials and methods Two expert panels of physiotherapists evaluated the assessments for content validity, while three physiotherapists evaluated inter-tester reliability. The assessments’ normative data from healthy participants were collected and compared to data from individuals on full sick leave due to MSK disorders. The participants on full sick leave included employees from healthcare, primary schools, and kindergartens. Results The expert panels considered the assessments as easy to administer, score, and relevant for their patients, aside from the ACR tender points test. Inter-tester reliability was high, with ICC2.1 values between 0.80 and 0.94, although two assessments showed high measurement error. Healthy participants performed significantly better on all assessments compared to those on full sick leave. Conclusion The assessments were generally considered relevant and beneficial in clinical practice when used for patients with MSK disorders. Five of the six assessments are valid and reliable for evaluating physical function in these patients and showed an excellent ability to discriminate between healthy individuals and those with MSK disorders on sick leave. These assessments have the potential to be useful in clinical practice, complementing a holistic evaluation of function and the ability to work. More research is needed to further explore their potential for assessing work participation and their applicability to different occupational groups.

Addressing measurement error in lobster growth modelling

Mark and recapture tagging data is key for determining growth in species that are hard or impossible to age. Obtaining this data can be an expensive process, consequently there is an increasing reliance on measurements from non-scientists including commercial and recreational fishers and industry volunteers. A challenge with relying on data collection from these groups is that they are likely to have higher measurement errors. We demonstrate that this measurement error can introduce substantial bias. To account for this we developed a Bayesian model that is robust to a broad range of measurement uncertainty, which enables stochasticity in model outputs to be attributed to more appropriate causes, such as environmental drivers for further investigation. The model was tested through application to Southern Rock Lobster (SRL), Jasus edwardsii data. This was applied in two distinct areas in Tasmania, with different biological characteristics and data collection regimes. Application to this case study demonstrates that high measurement error can be problematic for commonly used methods, however our developed approach allows unbiased growth estimation from such datasets.

Validity, Reliability, and Feasibility of Smartphone Application Intended for Home Measurement of Gait Speed and Other Gait Dynamics in Older Adults with Blood Cancers

Introduction: Gait speed is a cardinal measure of mobility and frailty recommended to be assessed in all older adults with cancer (Dale, JCO, 2023). Four-meter gait speed (4MGS) is strongly predictive of mortality and hospitalization in older adults with hematologic malignancies (Liu, Blood, 2019). Remote monitoring technology can expand measurement of gait speed beyond the clinic (Clancy, JCO CCI, 2023), and smartphone applications (App) have been developed and validated to measure meaningful gait metrics via embedded internal motion sensors (Manor, JMIR Mhealth Uhealth, 2018). However, the validity and reliability of a smartphone App for remotely measuring gait speed in older adults is not known, nor is the feasibility of using an App to measure longitudinal gait speed in older adults with blood cancers. Methods: We conducted two studies to (1) determine the validity and reliability of a smartphone App in measuring 4MGS in community-dwelling older adults, and (2) determine the feasibility of measuring 4MGS weekly for six weeks in older adults with multiple myeloma (MM) and myelodysplastic syndromes (MDS). For the validity and reliability study, we enrolled adults aged ≥ 65 years living in an independent living housing facility. Each participant self-administered two supervised and three unsupervised gait assessments at home via the smartphone carried in their pocket, with the App providing multimedia instructions on how to complete the test. For each gait assessment, the participants walked back and forth along a 4-meter strip of ribbon for 45 seconds. For the first two supervised sessions, while the participants were self-administering the gait assessment, the study team concurrently captured their walking performance with a video camera (as a gold standard). For the following three unsupervised sessions, the participants administered the gait assessment App alone. We obtained the time for the first instance of walking along the 4-meter ribbon before turning and compared the gait speed (i.e. dividing 4 meters by the time) between the smartphone and the video capture. For the feasibility study, we enrolled patients age ≥73 years with either MDS or MM cared for at Dana-Farber Cancer Institute. Patients self-administered the gait assessment described above alone at home once a day for six weeks after a dedicated teaching session with study staff. We reported completion rates and participants' feedback regarding acceptability. Results: 14 older adults (77.2±6.3, 13 females) completed the validity and reliability study. The smartphone 4MGS demonstrated strong criterion validity yielding a high correlation with the camera 4MGS ( Figure 1) along with high reliability as demonstrated by high internal consistency and low measurement error ( Figure 2). The smartphone 4MGS also showed good test-retest reliability over three unsupervised sessions (intra-class correlation coefficient 0.78). In the feasibility study, 12 patients (79.3±3.14, 4 females, 50% MDS, 42% MM, and 8% both) were enrolled out of 19 contacted for recruitment (63%). To date, nine have completed the study: 9/9 completed at least one 4MGS test, 8/9 (89%) completed at least three weeks, and 3/9 (33%) completed all six weeks. When asked, “How important is measuring your function and mobility to you?” on a scale of 1 (low) to 5 (high), 7/9 participants answered 4 or 5. When asked to rate their experience completing the walking tests on a scale of 1 (very poor) to 5 (very good), 6/9 participants answered 4 or 5. When asked the degree to which one agrees with the statement, “I feel that the walking tests are too burdensome,” on scale of 1 (strongly disagree) to 5 (strongly agree), 9/9 patients answered 1 or 2. Conclusions: The App was both valid and reliable in measuring 4MGS in older adults' homes. User acceptance was also high, and the app was rated as minimally burdensome by patients with blood cancers with the majority completing at least three weekly home 4MGS tests. Our findings support using existing smartphone technology to assess a key measure of mobility and frailty in the homes of older adults with blood cancers, allowing for more frequent longitudinal assessment of how blood cancers and their treatments impact older adult mobility and frailty.

Combining computer vision and standardised protocols for improved measurement of live sea urchins for research and industry

AbstractTo allow sea urchin aquaculture to achieve its intended scale, efficient and precise methods for measuring large numbers of urchins in commercial‐scale operations are needed. Current protocols for measuring urchin test (shell) dimensions and mass are time‐consuming and prone to high measurement error, thus inconvenient in research and impractical in a commercial context. This study investigates and compares various measurement methods with a newly developed computer vision approach developed in this study, to establish a single protocol using precise, efficient and accessible methodology for measuring live urchins. We show that urchin wet mass can vary up to 8.73% depending on time out of water; this is significantly reduced to an average of 0.1% change by allowing urchins to drip‐dry for at least 90 s prior to weighing. We found the conventional vernier calliper method used to measure urchin dimensions to be both time‐consuming and imprecise (mean coefficient of variation (CV) of 2.41% for Tripneustes gratilla). Conversely, the computer vision programme we developed measures with higher precision (mean CV of 1.55% for T. gratilla) and is considerably faster. The software uses a series of hue saturation value filters, edge detection algorithms and distortions to measure the diameter of the test (excluding spines) of multiple urchins at once. The software is open‐source, and the protocol does not require specialised equipment (can be performed with a mobile phone camera). When the computer vision application is combined with the simple procedures described in this paper, to reduce measurement inaccuracies, urchin wet mass and diameter can be more efficiently and precisely determined. For a larger scale context, this software could easily be incorporated into various tools, such as a grading machine, to completely automate various farm processes. As such, this study has potential to assist urchin data collection in both research and commercial contexts.

Capacity planning with limited information

Limited information about the demand for some of the resources needed to produce goods and services (e.g., incomplete and imperfect bills of materials) forces firms to use heuristics when planning resource capacity. We examine the performance of five heuristics: two drawn from practice, two that modify observed approaches, and one motivated by theory. We measure performance as the ratio of the expected cost of supply–demand mismatch from using a heuristic to the value in the full‐information solution. Numerical analysis shows that a simple heuristic that is common in practice—plan rigorously for a few “driver” resources with high‐quality information and use ratios (e.g., 0.25 indirect labor hours per machine hour) to project the capacities for the remaining “non‐driver” resources—is robust and efficient. Using more than one driver resource to plan for the same non‐driver resource delivers significant gains. Reducing measurement error with respect to the consumption of driver resources dominates the gain from reducing errors in other aspects. Indeed, with high measurement error, collecting information that reduces other sources of error could decrease overall performance. Finally, a greedy algorithm of choosing the most expensive resources as drivers is optimal.

Cell-type-specific co-expression inference from single cell RNA-sequencing data

The advancement of single cell RNA-sequencing (scRNA-seq) technology has enabled the direct inference of co-expressions in specific cell types, facilitating our understanding of cell-type-specific biological functions. For this task, the high sequencing depth variations and measurement errors in scRNA-seq data present two significant challenges, and they have not been adequately addressed by existing methods. We propose a statistical approach, CS-CORE, for estimating and testing cell-type-specific co-expressions, that explicitly models sequencing depth variations and measurement errors in scRNA-seq data. Systematic evaluations show that most existing methods suffered from inflated false positives as well as biased co-expression estimates and clustering analysis, whereas CS-CORE gave accurate estimates in these experiments. When applied to scRNA-seq data from postmortem brain samples from Alzheimer’s disease patients/controls and blood samples from COVID-19 patients/controls, CS-CORE identified cell-type-specific co-expressions and differential co-expressions that were more reproducible and/or more enriched for relevant biological pathways than those inferred from existing methods.

ЕФЕКТИВНІСТЬ ЗАСТОСУВАННЯ СИСТЕМ WIM НА АВТОМОБІЛЬНИХ ДОРОГАХ

Introduction. The introduction to the paper highlights the general role of the weight control of motor vehicles on roads by WiM – methods (Wegh-in-Motion) in the assurance of the traffic safety and in the transportation infrastructure preservation. Problem statement. The issues of the paper concern the problems of implementation of contemporary technologies of the High-Speed WiM (HS-WiM) where the conditions of the measurements of the loads from the vehicle generate high measurement error. Purpose. The main goal of the paper is to perform an analytical review of methods of the weight control of vehicles and of competitive aspects of existing WiM technologies and also the analysis of the practice of WiM application. Results. The analytical reviewing led to the following results: it was revealed that the basic principle of WiM systems operation consists in determining the dynamic wheel/axle loading of a vehicle transmitted to the pavement; data thus obtained shall be used to reveal the overloading. Modern WiM systems give possibilities to obtain data concerning axle number, axle spaces, vehicle length and speed, axle (or wheel) dynamic loading, number of equivalents of standard axle loading, and also data regarding the traffic flow characteristics; it was concluded that WiM systems can be divided into two main types: the systems operating at low speed of a vehicle (up to 15 km/h, LS WiM) and those operating at steady speed of the traffic flow (up to 130 km/h, or high speed, HS WiM). LS WiM ensure the accuracy of the measurement in a range from 3 % to 5 % and belong to the methods of weight control of motor vehicles approved by the legal metrology as well as the static weighing does. HS WiM control is more sensitive to the external factors due to the effect of a vehicle dynamic and thus cannot assure the above stated accuracy of measurements, moreover, cannot assure the appropriate accuracy for the satisfactory number of trucks. HS WiM systems are not approved by the legal metrology; factors affecting the accuracy of measurements in HS WiM systems were analyzed. It was revealed that the effect of a vehicle dynamic on the measurement error can be mitigated assuring the compliance of the road pavement surface condition with the standard requirements mainly with those concerning pavement surface roughness.

Dynamic Zero Current Method to Reduce Measurement Error in Low Value Resistive Sensor Array for Wearable Electronics.

One advantage of a resistive sensor array (RSA) with shared rows (M) and shared columns (N) is the reduced number of wires from M × N + 1 to M + N which can greatly lessen the complexity and burden on wearable electronic systems. However, the drawback is the crosstalk current effect between adjacent elements, which will lead to high measurement error. Although several solutions have been reported, they mainly focus on RSAs with high resistance (≥100 Ω). There is a lack of research that addresses RSAs with resistor values below 100 Ω. Here, we introduce a new circuit design named the dynamic zero current method (DZCM) to further decrease the measurement error. From the low value RSA test with ideal resistors, the DZCM exhibits lower error than the zero potential method (ZPM). In the case of the error variation ratio of amplifier offset voltage, the DZCM has a 4%/mV (row) to 7%/mV (column) ratio, while the ZPM has an almost 25%/mV (row) to 45%/mV (column) ratio and it increases with array size.

Using the bar-velocity to predict the one-repetition maximum in the power clean from the knee

This study investigated the predictive validity and reliability of the load-velocity relationship with the one-repetition maximum test (1RM) in power clean from the knee exercise (PC). Initially, 12 healthy young males, with no PC experience, underwent eight sessions to learn the PC technique. After the learning period, the participants visited the laboratory on four more occasions with intervals between the visits from 72 to 96 h. The first two sessions were dedicated to the actual 1RM tests, while the last two sessions were performed to measure the barbell’s load-velocity relationship at 30%, 45%, 60%, 75%, and 90% of PC 1RM. The highest peak velocity recorded at each load was used to establish the linear regression equation and, consequently, to predict 1RM values. As a result, a low validity was observed between the highest actual 1RM value and the predicted 1RM in sessions 1 and 2 (typical errors = 3.6 to 5.0 kg, coefficients of variation = 6.03 to 8.21%, effect sizes = -1.23 to -1.00, and Bland-Altman bias = 8.5 to 11.7 kg). For reliability, higher measurement errors (intraclass correlation coefficient, typical error, coefficient of variation, and width of limits of agreement at 95%) were observed for the predicted 1RM compared to the actual 1RM test. In conclusion, the load-velocity relationship was not able to predict the 1RM value with high accuracy in the PC from the knee. Moreover, the predicted 1RM presented inferior reliability than the actual 1RM test.

Аналіз методів та засобів вимірювання вологості сипких продуктів

Various methods of grain moisture measurement are considered in the article. The authors conducted the analysis of the conventional and modern methods of grain moisture measurement used in agriculture and the food industry. The principles of operation and the advantages and disadvantages of each method are described. The article examines in detail the methods used in international standards, and also analyzes the latest methods of grain moisture measurement, such as methods using infrared and microwave technology. The paper proposes a classification of methods for measuring the moisture content of bulk products and identifies the most relevant options for further research. Methods and means of grain moisture control are studied. The work established that the choice of grain moisture measurement method should depend on various factors, such as grain type, measurement accuracy, speed and cost of equipment. The authors analyzed each method in detail and made recommendations for choosing the optimal method of grain moisture measurement for specific conditions. The analysis was carried out and significant parameters affecting grain moisture measurements were selected. A comparison of the characteristics of hygrometers implemented by well-known ultra-high-frequency methods was carried out. The accuracy and errors of moisture measurement of significantly depends on the density of materials and indicators of the measurement medium. The considered hygrometers have high measurement error that does not meet the requirements of certain productions. The comparison of these parameters enabled to determine the optimal method for accurate moisture measurement.

Characterising the intensity of insecticide resistance: A novel framework for analysis of intensity bioassay data

Insecticide resistance is a growing problem that risks harming the progress made by vector control tools in reducing the malaria burden globally. New methods for quantifying the extent of resistance in wild populations are urgently needed to guide deployment of interventions to improve disease control. Intensity bioassays measure mosquito mortality at a range of insecticide doses and characterise phenotypic resistance in regions where resistance is already detected. These data are increasingly being collected but tend to exhibit high measurement error and there is a lack of formal guidelines on how they should be analysed or compared. This paper introduces a novel Bayesian framework for analysing intensity bioassay data, which uses a flexible statistical model able to capture a wide variety of relationships between mortality and insecticide dose. By accounting for background mortality of mosquitoes, our approach minimises the impact of this source of measurement noise resulting in more precise quantification of resistance. It outputs a range of metrics for describing the intensity and variability in resistance within the sample and quantifies the level of measurement error in the assay. The functionality is illustrated with data from laboratory-reared mosquitoes to show how the lethal dose varies within and between different strains. The framework can also be used to formally test hypotheses by explicitly considering the high heterogeneity seen in these types of data in field samples. Here we show that the intensity of resistance (as measured by the median lethal dose (LC50) of insecticide) increases over 7 years in mosquitoes from one village in Burkina Faso but remains constant in another. This work showcases the benefits of statistically rigorous analysis of insecticide bioassay data and highlights the additional information available from this and other dose-response data.

Validity and reliability of a portable handheld dynamometer compared to a fixed isokinetic dynamometer to assess forearm torque strength

To evaluate the effect of treatment on forearm rotation, torque muscle strength can be assessed using an isokinetic device (IKD) or a wrist dynamometer (WD). The aims of this study were 1) to determine concurrent validity and intra- and inter-rater reliability using the WD, and to examine correlations between WD and IKD in different positions; and 2) subsequently, to establish the intermethod reproducibility between WD as a handheld (HHD) or fixed device. We conducted a cross-sectional study in which torque strength was measured in healthy participants by two observers using an IKD and a WD. Study endpoints were concurrent validity (Pearson’s r), intra- and inter-rater reliability, intermethod reproducibility (intraclass correlation coefficient: ICC) and measurement error (limits of agreement: LoA). Concurrent validity ranged, in the 2 studies assessing it, from r 0.37 to 0.52 for pronation and from r 0.50 to 0.82 for supination, with wide 95% confidence intervals. ICC for intra-rater reliability for pronation ranged from 0.85 to 0.91 and for supination from 0.91 to 0.95. ICC for inter-rater reliability for pronation ranged from 0.84 to 0.96 and for supination from 0.92 to 0.96. Despite the excellent intra- and inter-rater reliability and intermethod reproducibility for the WD-HHD and fixed WD, validity was low when compared to IKD and wide LoA indicated a high measurement error of approximately 20%. These results suggest that the WD cannot replace the IKD isometric mode for pronation and supination. Level of evidence2.

Design of cable pipeline fault location device based on dynamic laser scanning

Aiming at the problem that some of the spare power cable pipelines without cable are damaged, and there is no effective detection equipment to detect the blocked state of the pipeline. This paper proposed a dynamic laser scanning method for obstacles in the pipeline, and designed a power pipeline fault positioning device. The infrared laser ranging technology based on time-of-flight is used to dynamically detect the distance between obstacles in the pipeline and the laser sensor, so as to detect the status and location of pipeline blockage. Taking ARM microcontroller as the core, equipped with VL53L0X laser module, the hardware design of the device was completed, and the software program was completed based on the Keil μVision5 IDE environment. The measurement and error analysis of obstacles of two different materials are carried out. The results show that the longer the measurement distance, the larger the error, and the highest measurement error is 1.47%, which fully meets the needs of engineering measurement.

Leg Length Measurement: Review

Background. Measurement of the length of the lower extremities is an important part of the assessment of the musculoskeletal system. If there is a discrepancy in the length of the legs, the accuracy of the measurement technique will determine the choice of further tactics for treating the patient. However, to date, there is no consensus among experts regarding the optimal and accurate method for assessing this clinical condition.
 The aim is to analyze foreign and domestic researches about measurement of limb length discrepancy and to determine the optimal method for measuring the lengths of the lower extremities.
 Methods. More than 70 scientific articles were selected from 1983 to 2021 in the PubMed/MEDLINE and eLIBRARY databases in Russian and English languages.
 Results. An analysis of the literature data did not reveal the optimal method for measuring the length of the lower extremities. Clinical evaluation procedures have demonstrated poor reproducibility and high measurement errors. Radiation imaging techniques also have measurement errors, additionally exerting radiation exposure on the patient. Imaging techniques such as ultrasound and MRI are described in several studies, which does not allow to fully determine all the advantages and disadvantages of these methods when measuring the lengths of the lower extremities.
 Conclusion. The study and development of new methods for diagnostics different lengths of the lower extremities, as well as the improvement of existing methods, will improve the quality of diagnosis of this pathological condition, and therefore affect the quality of the treatment for its correction.

Effects of pelvic obliquity and limb position on radiographic leg length discrepancy measurement: a Sawbones model

PurposePotential sources of inaccuracy in leg length discrepancy (LLD) measurements commonly arise due to postural malalignment during radiograph acquisition. Preoperative planning techniques for total hip arthroplasty (THA) are particularly susceptible to this inaccuracy, as they often rely solely on radiographic assessments. Owing to the extensive variety of pathologies that are associated with LLD, an understanding of the influence of malpositioning on LLD measurement is crucial. In the present study, we sought to characterize the effects of varying degrees of lateral pelvic obliquity (PO) and mediolateral limb movement in the coronal plane on LLD measurement error (ME).MethodsA 3-D sawbones model of the pelvis with bilateral femurs of equal-length was assembled. Anteroposterior pelvic radiographs were captured at various levels of PO: 0°, 5°, 10°, and 15°. At each level of PO, femurs were individually rotated medio-laterally to produce 0°, 5°, 10°, and 15° of abduction/adduction. LLD was measured radiographically at each position combination. For all cases of PO, the right-side of the pelvis was designated as the higher-side, and the left as the lower-side.ResultsAt 0° PO, 71% of tested variations in femoral abduction/adduction resulted in LLD ME < 0.5-cm, while 29% were ≥ 0.5-cm, but < 1-cm. ME increased progressively as one limb was further abducted while the contralateral limb was simultaneously further adducted. The highest ME occurred with one femur abducted 15° and the other adducted 15°. Similar magnitudes of ME were seen in 98% of tested femoral positions at 5° of PO. The greatest ME (~ 1 cm) occurred at the extremes of right-femur abduction and left-femur adduction. At 10° of PO, a higher prevalence of cases exhibited LLD ME > 0.5-cm (39%) and ≥ 1-cm (8%). The greatest errors occurred at femoral positions similar to those seen at 5° of PO. At 15° of PO, half of tested variations in femoral position resulted in LLD ME > 1-cm, while 22% of cases produced errors > 1.5-cm. These clinically significant errors occurred at all tested variations of right-femur abduction, with the left-femur in either neutral position, abduction, or adduction.ConclusionThis study aids surgeons in understanding the magnitude of radiographic LLD ME produced by varying degrees of PO and femoral abduction/adduction. At a PO of ≤5°, variations in femoral abduction/adduction of up to 15° produce errors of marginal clinical significance. At PO of 10° or 15°, even small changes in mediolateral limb position led to clinically significant ME (> 1-cm). This study also highlights the importance of proper patient positioning during radiograph acquisition, demonstrating the need for surgeons to assess the quality of their radiographs before performing preoperative templating for THA, and accounting for PO (> 5°) when considering the validity of LLD measurements.

On the reliability of individual economic rationality measurements

A contemporary research agenda in behavioral economics and neuroeconomics aims to identify individual differences and (neuro)psychological correlates of rationality. This research has been widely received in important interdisciplinary and field outlets. However, the psychometric reliability of such measurements of rationality has been presumed without enough methodological scrutiny. Drawing from multiple original and published datasets (in total over 1,600 participants), we unequivocally show that contemporary measurements of rationality have moderate to poor reliability according to common standards. Further analyses of the variance components, as well as a allowing participants to revise previous choices, suggest that this is driven by low between-subject variance rather than high measurement error. As has been argued previously for other behavioral measurements, this poses a challenge to the predominant correlational research designs and the search for sociodemographic or neural predictors. While our results draw a sobering picture of the prospects of contemporary measurements of rationality, they are not necessarily surprising from a theoretical perspective, which we outline in our discussion.