For the past 25 years, methodological advances have been made in missing data treatment. Most published work has focused on missing data in dependent variables under various conditions. The present study seeks to fill the void by comparing two approaches for handling missing data in categorical covariates in logistic regression: the…

Increasing working memory (WM) capacity is often cited as a major influence on children's development and yet WM capacity is difficult to examine independently of long-term knowledge. A computational model of children's nonword repetition (NWR) performance is presented that independently manipulates long-term knowledge and WM capacity to determine…

This paper presents an overview of how circuit models can be used for analysing wave propagation in stratified structures. Relatively complex structures can be analysed using models which are accessible to undergraduate students. Homogeneous slabs are modelled as transmission lines, and thin sheets between the slabs are modelled as lumped…

Systems thinking is an essential cognitive skill that enables individuals to develop an integrative understanding of a given subject at the conceptual and systemic level. Yet, systems thinking is not usually an innate skill. Helping students develop systems-thinking skills warrants attention from educators. This paper describes a study examining…

This paper examines the use of mixed methods for analyzing users' avatar-related activities in a virtual world. Server logs recorded keystroke-level activity for 595 participants over a six-month period in Whyville.net, an informal science website. Participants also completed surveys and participated in interviews regarding their experiences.…

Second Life[TM], or simply SL, was developed at Linden Lab, a San Francisco-based corporation defined by its creators as "an online society within a 3-D virtual world entirely built and owned by its residents, where they can explore, build, socialize and participate in their own economy." With over 14 million residents in the SL virtual community,…

We evaluated the statistical power of single-indicator latent growth curve models to detect individual differences in change (variances of latent slopes) as a function of sample size, number of longitudinal measurement occasions, and growth curve reliability. We recommend the 2 degree-of-freedom generalized test assessing loss of fit when both…

In this paper, we develop a conceptual framework for an anthropomorphic change agent to motivate pre-service teachers to integrate technology into teaching and learning. This agent is designed with a hybrid persona that simulates a mentor and plays both motivation and companion roles. Based on the theoretical grounding in motivation and change…

Orlando and Thissen (2000) developed an item fit statistic for binary item response theory (IRT) models known as S-X[superscript 2]. This article generalizes their statistic to polytomous unfolding models. Four alternative formulations of S-X[superscript 2] are developed for the generalized graded unfolding model (GGUM). The GGUM is a…

The CACTUS project was concerned with command and control training of large incidents where public order may be at risk, such as large demonstrations and marches. The training requirements and objectives of the project are first summarized justifying the use of knowledge-based computer methods to support and extend conventional training…

Person fit is the degree to which an item response model fits for individual examinees. Reise (2000) described how two-level logistic regression can be used to detect heterogeneity in person fit, evaluate potential predictors of person fit heterogeneity, and identify potentially aberrant individuals. The method has apparently never been applied to…

This article considers two methods of estimating standard errors of equipercentile equating: the parametric bootstrap method and the nonparametric bootstrap method. Using a simulation study, these two methods are compared under three sample sizes (300, 1,000, and 3,000), for two test content areas (the Iowa Tests of Basic Skills Maps and Diagrams…

In this qualitative pilot study, the authors report on curriculum field trials within a personal learning environment (PLE) designed by a collaboration of academic researchers and nonprofit volunteers working together in the virtual world of Second Life. The purpose of the PLE is to provide learners less likely to have access to educational…

Critical Chains project management focuses on holding buffers at the project level vs. task level, and managing buffers as a project resource. A number of studies have shown that Critical Chain project management can significantly improve organizational schedule fidelity (i.e., improve the proportion of projects delivered on time) and reduce…

"Harvard Education Letter" is published bimonthly at the Harvard Graduate School of Education. This issue of "Harvard Education Letter" contains the following articles: (1) Online Testing, Version 1.0: Oregon's Adaptive Computer-Based Accountability Test Offers a Peek at a Brave New Future (Robert Rothman); (2) Beyond…