Heterogeneity Coefficients for Mahalanobis' D as a Multivariate Effect Size

The Mahalanobis distance D is the multivariate generalization of Cohen's d and can be used as a standardized effect size for multivariate differences between groups. An important issue in the interpretation of D is heterogeneity, that is, the extent to which contributions to the overall effect size are concentrated in a small subset of variables rather than evenly distributed across the whole set. Here I present two heterogeneity coefficients for D based on the Gini coefficient, a well-known index of inequality among values of a distribution. I discuss the properties and limitations of the two coefficients and illustrate their use by reanalyzing some published findings from studies of gender differences.     

大学生网络成瘾量表（修订版）的多元概化分析*

用多元概化理论考察大学生网络成瘾量表在大学生群体中应用的测量学性能。以随机测量模式的概化设计,针对1200名在校大学生进行问卷调查。结果显示双因子结构的相关程度在0.92以上,五因子结构的相关程度均在0.76~0.97间;整体量表的概化系数和可靠性指数均达到了0.94以上,而双因子结构各因子在0.90左右,五因子结构各因子均在0.74~0.85间。所以,整体量表及各因子在大学生群体中应用的信效度较高,可用作常模和标准参照测验;无论双因子还是五因子结构,CIAS-R各因子在分值比和项目数上,设计非常合理和完善。     

Games of luck and games of chance: the effect of luck- versus chance-orientation on gambling decisions

Chance and luck are conceived as two distinct causal agents that effect different results. The present study examined the proposition that persons who habitually attribute the outcome of random events to chance (chance-oriented persons) and those who prefer to attribute such outcomes to luck (luck-oriented persons) cope differently with decision making under uncertainty. Chance-oriented persons decide according to given or estimated odds that define the decision problem. Luck-oriented persons, on the other hand, rely on self-attributions of personal luck, and ignore the probabilities of decision outcomes. The hypothesized qualitative difference between the approaches of chance- and luck-oriented persons to decision making under uncertainty was supported substantially by the findings. © 1998 John Wiley & Sons, Ltd.     

Adjusting for information inflation due to local dependency in moderately large item clusters

When multiple items are clustered around a reading passage, the local independence assumption in item response theory is often violated. The amount of information contained in an item cluster is usually overestimated if violation of local independence is ignored and items are treated as locally independent when in fact they are not. In this article we provide a general method that adjusts for the inflation of information associated with a test containing item clusters. A computational scheme was presented for the evaluation of the factor of adjustment for clusters in the restrictive case of two items per cluster, and the general case of more than two items per cluster. The methodology was motivated by a study of the NAEP Reading Assessment. We present a simulated study along with an analysis of a NAEP data set.The research was supported under the National Assessment of Educational Progress (Grant No. R999G30002) as administered by the Office of Educational Research and Improvement, U.S. Department of Education. This work was started when the author was at the Division of Statistics and Psychometrics at the Educational Testing Service. The author thanks Juliet Shaffer, Bob Mislevy, Eric Bradlow, three reviewers and an associate editor for their helpful comments on the paper.     

An interactive procedure for learning about preferences: Case study of a portfolio manager

This paper presents a new interactive procedure for learning and interpreting the choices available to a decision maker confronted with a discrete decision problem. The procedure guides a decision maker through the evaluation process, has an ability ‘to learn’ from previous choices and generates a set of rules that describe a decision maker's posterior preferences. The validity of the procedure was tested by creating an investment portfolio. The emphasis of the application is on assisting the portfolio manager to determine the decision consistency of a given portfolio selection process.     

Thinking about decisions: An integrative approach of person and task factors

Decisions vary. They may vary in both content and complexity. People also vary. An important way that people vary is how much they think. Some prior research investigating thinking and decision making largely conflicts with most traditional decision theories. For example, if considering an array of products to choose from, thinking more about the alternative's attributes should lead to a better decision. However, some research indicates that thinking more may also lead to focusing on irrelevant aspects of the decision and a less optimal outcome. We propose that this conflict in the literature exists because of a failure to consider the interaction between the individual and the decision task. To test this, we used separate methodologies that enhance or attenuate a person's thinking. In Study 1, we selected people who were especially high or low in need for cognition and had them complete a robust decision-making inventory, which included both complex and simple tasks. In Study 2, we manipulated participant's level of glucose, which acts as the brain's fuel to enhance or attenuate thinking ability. Both studies provide insight for understanding our central tenant that more thought leads to better decisions in complex tasks but does not influence simple decisions. These findings show how the individual's thinking can interact with the constructive elements of the task to shape decision choice.     

Brain activity patterns of phonemic representations are atypical in beginning readers with family risk for dyslexia

There is an ongoing debate whether phonological deficits in dyslexics should be attributed to (a) less specified representations of speech sounds, like suggested by studies in young children with a familial risk for dyslexia, or (b) to an impaired access to these phonemic representations, as suggested by studies in adults with dyslexia. These conflicting findings are rooted in between study differences in sample characteristics and/or testing techniques. The current study uses the same multivariate functional MRI (fMRI) approach as previously used in adults with dyslexia to investigate phonemic representations in 30 beginning readers with a familial risk and 24 beginning readers without a familial risk of dyslexia, of whom 20 were later retrospectively classified as dyslexic. Based on fMRI response patterns evoked by listening to different utterances of /bA/ and /dA/ sounds, multivoxel analyses indicate that the underlying activation patterns of the two phonemes were distinct in children with a low family risk but not in children with high family risk. However, no group differences were observed between children that were later classified as typical versus dyslexic readers, regardless of their family risk status, indicating that poor phonemic representations constitute a risk for dyslexia but are not sufficient to result in reading problems. We hypothesize that poor phonemic representations are trait (family risk) and not state (dyslexia) dependent, and that representational deficits only lead to reading difficulties when they are present in conjunction with other neuroanatomical or—functional deficits.