Monitoring Item Performance With CUSUM Statistics in Continuous Testing

2021 ◽  
pp. 107699862199456
Author(s):  
Yi-Hsuan Lee ◽  
Charles Lewis
Keyword(s):  
Group Size ◽  
Estimation Error ◽  
Ability Estimation ◽  
Cumulative Sum ◽  
Continuous Testing ◽  
Item Parameters ◽  
Analytical Work ◽  
Educational Assessments ◽  
Over Time ◽  
Item Preknowledge

In many educational assessments, items are reused in different administrations throughout the life of the assessments. Ideally, a reused item should perform relatively similarly over time. In reality, an item may become easier with exposure, especially when item preknowledge has occurred. This article presents a novel cumulative sum procedure for detecting item preknowledge in continuous testing where data for each reused item may be obtained from small and varying sample sizes across administrations. Its performance is evaluated with simulations and analytical work. The approach is effective in detecting item preknowledge quickly with group size at least 10 and is easy to implement with varying item parameters. In addition, it is robust to the ability estimation error introduced in the simulations.

AN EMPIRICAL STUDY INTO THE ACCURACY OF IT ESTIMATIONS AND ITS INFLUENCING FACTORS

2013 ◽  
Vol 23 (04) ◽  
pp. 409-432 ◽  
Author(s):  
A. H. ZAPATA ◽  
M. R. V. CHAUDRON
Keyword(s):  
Estimation Error ◽  
Software Project ◽  
Learning Improvement ◽  
Current Estimation ◽  
It Department ◽  
Improvement Effect ◽  
Different Dimensions ◽  
Effectiveness And Efficiency ◽  
Process Complexity ◽  
Over Time

This paper is the result of two related studies done on the estimation of IT projects at a large Dutch multinational company. The first one is a study about the accuracy of different dimensions of IT project estimating: schedule, budget and effort. [Note: This paper is an extension of the paper published by the authors as "An analysis of accuracy and learning in software project estimating" [28].] This study is based on a dataset of 171 projects collected at the IT department of the company. We analyzed the estimation error of budget, effort and schedule. Also, we analyzed whether there is any learning (improvement) effect over time. With the results of the first study we proceeded to research what is causing the current estimation error (inaccuracy). The results of our first study show that there is no relation between accuracy of budget, schedule and effort in the company analyzed. Besides, they show that over time there is no change in the inaccuracy (effectiveness and efficiency of the estimates). In our second study we discovered that the sources of this inaccuracy are: (IT estimation) process complexity, misuse of estimates, technical complexity, requirements redefinition and business domain instability. This paper reflects and provides recommendations on how to improve the learning from historical estimates and how to manage the diverse sources of inaccuracy inside this particular company and also in other organizations.

scholarly journals Desempenho Fora-da-Amostra da Otimização Robusta de Carteiras

2010 ◽  
Vol 8 (2) ◽  
pp. 141 ◽  
Author(s):  
André Alves Portela Santos
Keyword(s):  
Robust Optimization ◽  
Portfolio Optimization ◽  
Estimation Error ◽  
Simulated Data ◽  
Minimum Variance ◽  
Optimization Techniques ◽  
Practical Implementation ◽  
Out Of Sample ◽  
Portfolio Optimization Problem ◽  
Over Time

Robust optimization has been receiving increased attention in the recent few years due to the possibility of considering the problem of estimation error in the portfolio optimization problem. A question addressed so far by very few works is whether this approach is able to outperform traditional portfolio optimization techniques in terms of out-of-sample performance. Moreover, it is important to know whether this approach is able to deliver stable portfolio compositions over time, thus reducing management costs and facilitating practical implementation. We provide empirical evidence by assessing the out-of-sample performance and the stability of optimal portfolio compositions obtained with robust optimization and with traditional optimization techniques. The results indicated that, for simulated data, robust optimization performed better (both in terms of Sharpe ratios and portfolio turnover) than Markowitz's mean-variance portfolios and similarly to minimum-variance portfolios. The results for real market data indicated that the differences in risk-adjusted performance were not statistically different, but the portfolio compositions associated to robust optimization were more stable over time than traditional portfolio selection techniques.

scholarly journals Stochastic imputation for integrated transcriptome association analysis of a longitudinally measured trait

2019 ◽  
Vol 29 (4) ◽  
pp. 1167-1180 ◽  
Author(s):  
Evan L Ray ◽  
Jing Qian ◽  
Regina Brecha ◽  
Muredach P Reilly ◽  
Andrea S Foulkes
Keyword(s):  
Association Analysis ◽  
Complex Disease ◽  
Estimation Error ◽  
Penalized Regression ◽  
Error Rates ◽  
Test Statistic ◽  
Modeling Framework ◽  
Two Stage ◽  
Regression Imputation ◽  
Over Time

The mechanistic pathways linking genetic polymorphisms and complex disease traits remain largely uncharacterized. At the same time, expansive new transcriptome data resources offer unprecedented opportunity to unravel the mechanistic underpinnings of complex disease associations. Two-stage strategies involving conditioning on a single, penalized regression imputation for transcriptome association analysis have been described for cross-sectional traits. In this manuscript, we propose an alternative two-stage approach based on stochastic regression imputation that additionally incorporates error in the predictive model. Application of a bootstrap procedure offers flexibility when a closed form predictive distribution is not available. The two-stage strategy is also generalized to longitudinally measured traits, using a linear mixed effects modeling framework and a composite test statistic to evaluate whether the genetic component of gene-level expression modifies the biomarker trajectory over time. Simulations studies are performed to evaluate relative performance with respect to type-1 error rates, coverage, estimation error, and power under a range of conditions. A case study is presented to investigate the association between whole blood expression for each of five inflammasome genes with inflammatory response over time after endotoxin challenge.

scholarly journals A Novel Technique for Identifying Patients with ICU Needs Using Hemodynamic Features

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
A. Jalali ◽  
P. Ghorbanian ◽  
A. Ghaffari ◽  
C. Nataraj
Keyword(s):  
Intensive Care ◽  
Healthy Subjects ◽  
Predictive Accuracy ◽  
Estimation Error ◽  
Autonomic Response ◽  
Membership Degree ◽  
Cumulative Sum ◽  
Scoring Method ◽  
Poincaré Plot ◽  
Hemodynamic Variables

Identification of patients requiring intensive care is a critical issue in clinical treatment. The objective of this study is to develop a novel methodology using hemodynamic features for distinguishing such patients requiring intensive care from a group of healthy subjects. In this study, based on the hemodynamic features, subjects are divided into three groups: healthy, risky and patient. For each of the healthy and patient subjects, the evaluated features are based on the analysis of existing differences between hemodynamic variables: Blood Pressure and Heart Rate. Further, four criteria from the hemodynamic variables are introduced: circle criterion, estimation error criterion, Poincare plot deviation, and autonomic response delay criterion. For each of these criteria, three fuzzy membership functions are defined to distinguish patients from healthy subjects. Furthermore, based on the evaluated criteria, a scoring method is developed. In this scoring method membership degree of each subject is evaluated for the three classifying groups. Then, for each subject, the cumulative sum of membership degree of all four criteria is calculated. Finally, a given subject is classified with the group which has the largest cumulative sum. In summary, the scoring method results in 86% sensitivity, 94.8% positive predictive accuracy and 82.2% total accuracy.

Estimating Linking Functions for Response Model Parameters

2018 ◽  
Vol 44 (2) ◽  
pp. 180-209 ◽  
Author(s):  
Michelle D. Barrett ◽  
Wim J. van der Linden
Keyword(s):  
Response Function ◽  
Estimation Error ◽  
Simple Calculation ◽  
Model Parameters ◽  
New Approach ◽  
Item Parameters ◽  
Superficial Similarity ◽  
The Mean ◽  
Common Items ◽  
Monotone Decrease

Parameter linking in item response theory is generally necessary to adjust for differences between the true values for the same item and ability parameters due to the use of different identifiability restrictions in different calibrations. The research reported in this article explores a precision-weighted (PW) approach to the problem of estimating the linking functions for the common dichotomous logistic response models. Asymptotic standard errors (ASEs) of linking for the new approach are derived and compared to those of the mean/mean and mean/sigma linking methods to which it has a superficial similarity and to the Haebara and Stocking and Lord response function methods. Empirical examples from a few recent linking studies are presented. It is demonstrated that the new approach has smaller ASE than the mean/mean and mean/sigma methods and comparable ASE to the response function methods. However, when some of the item parameters have large estimation error relative to the others, all current methods appear to violate the rather obvious requirement of monotone decrease in ASE with the number of common items in the linking design while the ASE of the PW method demonstrates monotone decrease with the number of common items. The PW method also has the benefits of simple calculation and an ASE which is additive in the contribution of each item, useful for optimal linking design. We conclude that the proposed approach to estimating linking parameters holds promise and warrants further research.

Investigating the Impact of Uncertainty About Item Parameters on Ability Estimation

Psychometrika ◽  
2011 ◽  
Vol 76 (1) ◽  
pp. 97-118 ◽  
Author(s):  
Jinming Zhang ◽  
Minge Xie ◽  
Xiaolan Song ◽  
Ting Lu
Keyword(s):  
Ability Estimation ◽  
Item Parameters ◽  
The Impact

scholarly journals Accuracy and Convergence Analysis of uFA-FastSLAM for Robot and Landmarks Position Estimation

2021 ◽  
Vol 2129 (1) ◽  
pp. 012018
Author(s):  
R J Musridho ◽  
H Hasan ◽  
H Haron ◽  
D Gusman ◽  
M A Mohammad
Keyword(s):  
Mobile Robots ◽  
Convergence Analysis ◽  
Firefly Algorithm ◽  
Estimation Error ◽  
Position Estimation ◽  
Autonomous Mobile Robots ◽  
Localization And Mapping ◽  
Robot Position ◽  
Modified Firefly Algorithm ◽  
Over Time

Abstract In autonomous mobile robots, Simultaneous Localization and Mapping (SLAM) is a demanding and vital topic. One of two primary solutions of SLAM problem is FastSLAM. In terms of accuracy and convergence, FastSLAM is known to degenerate over time. Previous work has hybridized FastSLAM with a modified Firefly Algorithm (FA), called unranked Firefly Algorithm (uFA), to optimize the accuracy and convergence of the robot and landmarks position estimation. However, it has not shown the performance of the accuracy and convergence. Therefore, this work is done to present both mentioned performances of FastSLAM and uFA-FastSLAM to see which one is better. The result of the experiment shows that uFA-FastSLAM has successfully improved the accuracy (in other words, reduced estimation error) and the convergence consistency of FastSLAM. The proposed uFA-FastSLAM is superior compared to conventional FastSLAM in estimation of landmarks position and robot position with 3.30 percent and 7.83 percent in terms of accuracy model respectively. Furthermore, the proposed uFA-FastSLAM also exhibits better performances compared to FastSLAM in terms of convergence consistency by 93.49 percent and 94.20 percent for estimation of landmarks position and robot position respectively.

scholarly journals A Method to Accurately Estimate Fish Abundance in Offshore Cages

2020 ◽  
Vol 10 (11) ◽  
pp. 3720
Author(s):  
Pranesh Sthapit ◽  
MinSeok Kim ◽  
Kiseon Kim
Keyword(s):  
Integration Method ◽  
Estimation Error ◽  
Fish Abundance ◽  
Water Current ◽  
Abundance Estimation ◽  
Integration Technique ◽  
Echo Signal ◽  
User Friendly ◽  
Reliable Methods ◽  
Over Time

Due to the lack of reliable methods, manual fish counting is popular on farms. However, this approach is time and labor intensive. Using an echosounder and the echo-integration technique could be a better alternative. The echo-integration method has been widely used in fish abundance estimation in waterbodies because of its simplicity. However, most of the research is concentrated on the open ocean, whereas fish count estimation in farming cages has not been explored much. Using the echo-integration method in a cage offers its own unique sets of problems. Firstly, the echo signal reflected from the cage boundaries should also be taken into account. Secondly, the fish inside a cage behave differently with time, as their mobility pattern is highly dependent on sunlight and water current. In this paper, fish behavior inside an offshore cage over time was extensively studied, and based on that a real-time fish counter system using a commercial echosounder was developed. The experiments demonstrate that our method is simple, user-friendly, and has an estimation error of less than 10%. Since our method accurately estimated fish abundance, the method should be reliable when making fish management decisions.

scholarly journals Anti-Predator Vigilance as an Indicator of the Costs and Benefits of Supplemental Feeding in Newly Released ‘Alalā (Corvus hawaiiensis)

2021 ◽  
Vol 2 ◽  
Author(s):  
Heather N. Lee ◽  
Alison L. Greggor ◽  
Bryce Masuda ◽  
Ronald R. Swaisgood
Keyword(s):  
Predation Risk ◽  
Group Size ◽  
Conservation Strategy ◽  
Food Sources ◽  
Supplemental Feeding ◽  
Costs And Benefits ◽  
Additional Food ◽  
Dynamic Decisions ◽  
Feeder Design ◽  
Over Time

Although supplemental feeding is commonly used as a conservation strategy during animal translocations, it comes with a number of pros and cons which can be hard to quantify. Providing additional food resources may lead to improved physical health, survivorship, and reproduction. However, offering predictable food sources could make individuals more conspicuous to predators and less aware of their surroundings, disrupting their natural predator-prey dynamic. Decisions such as release cohort size and supplemental feeder design could influence the balance of these costs and benefits, depending on how animals behave in the face of predation risk and static food sources. Additionally, animals released to the wild from long term human care must balance foraging and predation risk while adjusting to a novel environment. To help conservation managers make informed decisions in light of these potential costs, we studied the behavior of a cohort of 11 conservation-bred ‘alalā (Corvus hawaiiensis) at supplemental feeding stations after release into the wild. Vigilance, foraging behavior and social group size was quantified via 1,320 trail camera videos of ‘alalā over the span of 12 months. We found that vigilance increased over time since release, suggesting that ‘alalā learn and adjust to their novel surroundings. Both vigilance and eating decreased with group size, indicating that although conspecifics may share the burden of scanning for threats, they also increase competition for food. We also found that the design of the feeder may have limited birds' abilities to express anti-predator behavior since less vigilance was observed in individuals that manipulated the feeder. Yet, birds may have been able to offset these costs since they increasingly scrounged for food scraps next to the feeder as time progressed. We discuss how changes to behavior over time, social interactions, and feeder design should all be considered when planning supplemental feeding as part of wildlife translocations.

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