GPCM模型项目参数估计程序的开发与研究

该文对GPCM的项目参数估计的方法进行较为深入的探讨,特别对容易混淆的参数初值计算以及项目参数分两步进行估计的原因进行了阐述。并且基于MMLE／EM算法,开发了相应的项目参数估计程序。通过大量的蒙特卡洛模拟,与国外专业软件PARSCALE比较,本程序的步骤参数估计值更好,区分度参数估计值相当,具有较好的应用价值。     

抗感染治疗的今天和明天

抗菌药物治疗是临床医学界普遍关切的问题。滥用抗生素的问题引起社会和政府的重视。但解决这问题需要重视调查研究,充分应用科学研究成果,制定科学合理的政策和规定。本文还从医生的角度,对经验用药、社区获得性肺炎治疗中的几个问题,介绍了国外的做法,对应用药代动力学和最低抑菌浓度结合的研究方法,包括Monte Carlo模拟的实验和临床研究,以及防突变浓度（MPC）和突变选择窗（MEw）的概念作了介绍。     

Bayesian estimation of a multilevel IRT model using gibbs sampling

In this article, a two-level regression model is imposed on the ability parameters in an item response theory (IRT) model. The advantage of using latent rather than observed scores as dependent variables of a multilevel model is that it offers the possibility of separating the influence of item difficulty and ability level and modeling response variation and measurement error. Another advantage is that, contrary to observed scores, latent scores are test-independent, which offers the possibility of using results from different tests in one analysis where the parameters of the IRT model and the multilevel model can be concurrently estimated. The two-parameter normal ogive model is used for the IRT measurement model. It will be shown that the parameters of the two-parameter normal ogive model and the multilevel model can be estimated in a Bayesian framework using Gibbs sampling. Examples using simulated and real data are given.     

A Monte Carlo method for comparing generalized estimating equations to conventional statistical techniques for discounting data

Discounting is the process by which outcomes lose value. Much of discounting research has focused on differences in the degree of discounting across various groups. This research has relied heavily on conventional null hypothesis significance tests that are familiar to psychologists, such as t‐tests and ANOVAs. As discounting research questions have become more complex by simultaneously focusing on within‐subject and between‐group differences, conventional statistical testing is often not appropriate for the obtained data. Generalized estimating equations (GEE) are one type of mixed‐effects model that are designed to handle autocorrelated data, such as within‐subject repeated‐measures data, and are therefore more appropriate for discounting data. To determine if GEE provides similar results as conventional statistical tests, we compared the techniques across 2,000 simulated data sets. The data sets were created using a Monte Carlo method based on an existing data set. Across the simulated data sets, the GEE and the conventional statistical tests generally provided similar patterns of results. As the GEE and more conventional statistical tests provide the same pattern of result, we suggest researchers use the GEE because it was designed to handle data that has the structure that is typical of discounting data.     

Perceived optimality of competing solutions to the Euclidean travelling salesperson problem

The Travelling Salesperson Problem (TSP) is a nondeterministic-polynomial hard (NP-hard) combinatorial problem that occurs in a wide range of industrial domains, including logistics, route finding, and computer wiring. Interestingly, despite the problem’s inherent computational difficulty, when presented in Euclidean space (ETSP), human participants can produce close-to-optimal solutions in near-linear time. However, when asked to compare and select the most optimum solution from a set of pre-defined competing solution options, participants can struggle. In this study we investigate this paradox by asking participants to compare four closed-loop Euclidean TSP solutions, in order to determine which solution they perceived to have the most optimal tour cost. We hypothesise that the extracted geometric properties have an effect on stimulus selection in a discrimination task (selection or no selection). Accordingly, we extracted four geometric properties from competing stimuli in order to create a perceptual activation function. Predictive analytics demonstrated that a classification model could identify the most optimal solution 97% of the time using the perceptual activation scores alone, yet human participants only correctly determined the most optimal solution 47% of the time. Mixed-effects models suggest that ‘likelihood of stimulus selection’ can be modelled as a function of the weighted coefficients of competing perceptual activation scores within each trial; however only a small amount of the variance is explained by these perceptual activation scores. Finally, a drift–diffusion model was used to create a theoretical framework of how likelihood of stimulus selection is influenced by competing perceptual activators. Our study highlights a novel way of extracting and analysing the importance of geometric properties that influence ETSP discrimination tasks, and links this analysis to human behaviour when discriminating between competing ETSP solutions.     

对齐法在单因子和三因子多组比较中允许的不等参数率

在传统的多组验证性因子分析中,进行因子均值比较的前提条件是模型满足强测量不变性假设,但该假设在实证研究中很难满足。这时,Asparouhov和Muthén(2014)提出的对齐法是一种可供备选的多组分析法。通过蒙特卡洛模拟研究,探究了在对齐法精确估计模型参数前提下所允许的不等参数率范围。研究发现：在平均组样本量充足,识别算法为固定识别算法等理想状态下,对齐法在单因子模型多组比较中所允许的不等参数率可以是100%;在三因子模型中所允许的不等参数率上限是20%至30%;在此范围内,对齐法允许更多高程度不等参数;在组数目从30、15或9降至3时,对齐法能允许更多的不等参数在模型中。     

Using Response Times for Joint Modeling of Response and Omission Behavior

Abstract

For adequate modeling of missing responses, a thorough understanding of the nonresponse mechanisms is vital. As a large number of major testing programs are in the process or already have been moving to computer-based assessment, a rich body of additional data on examinee behavior becomes easily accessible. These additional data may contain valuable information on the processes associated with nonresponse. Bringing together research on item omissions with approaches for modeling response time data, we propose a framework for simultaneously modeling response behavior and omission behavior utilizing timing information for both. As such, the proposed model allows (a) to gain a deeper understanding of response and nonresponse behavior in general and, in particular, of the processes underlying item omissions in LSAs, (b) to model the processes determining the time examinees require to generate a response or to omit an item, and (c) to account for nonignorable item omissions. Parameter recovery of the proposed model is studied within a simulation study. An illustration of the model by means of an application to real data is provided.