Expanding the rasch model to a general model having more than one dimension

The well-known Rasch model is generalized to a multicomponent model, so that observations of component events are not needed to apply the model. It is shown that the generalized model has retained the property of the specific objectivity of the Rasch model. For a restricted variant of the model, maximum likelihood estimates of its parameters and a statistical test of the model are given. The results of an application to a mathematics test involving six components are described.     

Testing sequence effects in visual memory: clues for a structural model

In order to probe the internal organization of visual temporary memory, systematic experiments were performed in which the subjects had to memorize a series of 2-5 images then pass recognition tests, either in all possible testing permutations, (in the case of 2-4 images) or in 20 selected permutations (in the case of 5 images). Over 300,000 tests were performed, generating more than 40,000 errors. The error-rates were found to follow simple rules. Both the 3 and the 4 images results are compatible with the presence of only four typical accuracy levels. On the other hand, the reaction time (RT) results revealed surprisingly rich patterns. The RT for recognizing image i at testing stage t > 1 depends upon which image (j) was tested just before. The ranking of the RTs for (j, i) couples evolves from one testing stage to the next. It is proposed that these RTs reflect, in part, the time needed to localize the trace in memory of a given image, starting from the position at which the previous test occurred. If this assumption is correct, the results of this study are providing a picture of the configurations formed by memorized items in the visual temporary store. A hypothetical minimal model, involving several rows of slots on a triangular mesh is proposed to account for the structures in both the error-rates and the RT results.     

Stochastic EM for estimating the parameters of a multilevel IRT model

An item response theory (IRT) model is used as a measurement error model for the dependent variable of a multilevel model. The dependent variable is latent but can be measured indirectly by using tests or questionnaires. The advantage of using latent scores as dependent variables of a multilevel model is that it offers the possibility of modelling response variation and measurement error and separating the influence of item difficulty and ability level. The two‐parameter normal ogive model is used for the IRT model. It is shown that the stochastic EM algorithm can be used to estimate the parameters which are close to the maximum likelihood estimates. This algorithm is easily implemented. The estimation procedure will be compared to an implementation of the Gibbs sampler in a Bayesian framework. Examples using real data are given.     

Reaction time analysis of two types of motor preparation for speech articulation: action as a sequence of chunks

Reaction time (RT) prior to speech articulation increased as a function of response complexity. The RT findings formed 2 patterns, each of which was a different Response Complexity x Paradigm (choice RT vs. simple RT) interaction. That result extends previous findings from manual button-pressing tasks (S. T. Klapp, 1995) to a different action modality. Two different types of response programming, INT and SEQ, are assumed in the interpretation. Whereas INT can be identified with response programming within a word, SEQ fits a different interpretation related to timing of onsets of speech units. A critical assumption is that a long response is represented as a sequence of chunks; that organization is subject to manipulation. New findings suggest some modifications of the previous theory.     

A general linear model for estimating effect size in the presence of publication bias

When the process of publication favors studies with smallp-values, and hence large effect estimates, combined estimates from many studies may be biased. This paper describes a model for estimation of effect size when there is selection based on one-tailedp-values. The model employs the method of maximum likelihood in the context of a mixed (fixed and random) effects general linear model for effect sizes. It offers a test for the presence of publication bias, and corrected estimates of the parameters of the linear model for effect magnitude. The model is illustrated using a well-known data set on the benefits of psychotherapy.Authors' note: The contributions of the authors are considered equal, and the order of authorship was chosen to be reverse-alphabetical.     

A sensitive rank test for comparing the effects of two treatments on a single group

By taking advantage of an experimental design which increases the number of observations per subject, the sensitivity of the proposed test is increased. In the first of a series of subexperiments, the score of a randomly selected experimentalS is ranked with the scores of the remaining (control)Ss, and the experimentalS is discarded. This procedure is repeated until oneS remains. The test criterion,R _n , is the sum of ranks of the experimentalSs; its exact sampling distribution, a normal approximation, and the sensitivity of the test relative to the WilcoxonT, are described. Because of the large number of scores obtained, the test is particularly useful when preparingSs is more costly than testing them, e.g., in tests following involved conditioning procedures. Since eachS is discarded after experimental treatment, the test fills a real need in studies involving radiation, ablation, or other irreversible treatments.The test criterion, the associated experimental procedure, and the measure of sensitivity are due to SHR; the generating function, tables, and large sample approximation are due to JNC.     

Long-term effects from a randomized trial of two public health preventive interventions for parental depression.

This article presents long-term effects of a randomized trial evaluating 2 standardized, manual-based prevention strategies for families with parental mood disorder: informational lectures and a brief, clinician-based approach including child assessment and a family meeting. A sample of 105 families, in which at least 1 parent suffered from a mood disorder and at least 1 nondepressed child was within the 8- to 15-year age range, was recruited. Parents and children were assessed separately at baseline and every 9 to 12 months thereafter on behavioral functioning, psychopathology, and response to intervention. Both interventions produced sustained effects through the 6th assessment point, approximately 4.5 years after enrollment, with relatively small sample loss of families (<14%). Clinician-based families had significantly more gains in parental child-related behaviors and attitudes and in child-reported understanding of parental disorder. Child and parent family functioning increased for both groups and internalizing symptoms decreased for both groups, with no significant group differences. These findings demonstrate that brief, family-centered preventive interventions for parental depression may contribute to long-term, sustained improvements in family functioning.     

Influence of stimulus type on effects of flanker,flanker position,and trial sequence in a saccadic eye movement task

Using the flanker paradigm in a task requiring eye movement responses, we examined how stimulus type (arrows vs. letters) modulated effects of flanker and flanker position. Further, we examined trial sequence effects and the impact of stimulus type on these effects. Participants responded to a central target with a left- or rightward saccade. We reasoned that arrows, being overlearned symbols of direction, are processed with less effort and are therefore linked more easily to a direction and a required response than are letters. The main findings demonstrate that (a) flanker effects were stronger for arrows than for letters, (b) flanker position more strongly modulated the flanker effect for letters than for arrows, and (c) trial sequence effects partly differed between the two stimulus types. We discuss these findings in the context of a more automatic and effortless processing of arrow relative to letter stimuli.     

A comparison of methods for estimating quadratic effects in nonlinear structural equation models

Two Monte Carlo simulations were performed to compare methods for estimating and testing hypotheses of quadratic effects in latent variable regression models. The methods considered in the current study were (a) a 2-stage moderated regression approach using latent variable scores, (b) an unconstrained product indicator approach, (c) a latent moderated structural equation method, (d) a fully Bayesian approach, and (e) marginal maximum likelihood estimation. Of the 5 estimation methods, it was found that overall the methods based on maximum likelihood estimation and the Bayesian approach performed best in terms of bias, root-mean-square error, standard error ratios, power, and Type I error control, although key differences were observed. Similarities as well as disparities among methods are highlight and general recommendations articulated. As a point of comparison, all 5 approaches were fit to a reparameterized version of the latent quadratic model to educational reading data.     

Intralanguage vs. interlanguage Stroop effects in two types of writing systems

The relation between word processing strategy and the orthographic structure of a written language was explored in the present study. Three experiments were conducted using Chinese-English, Spanish-English, and Japanese-English bilinguals, respectively. Each subject was asked to perform a modified Stroop color-naming task in which the stimulus and the response language were either the same or different. The magnitude of the Stroop effect was greater in the intralanguage condition than in the interlanguage condition. When the magnitude of reduction of Stroop interference from the intra- to the interlanguage condition was compared across all bilingual groups, an inverse relationship was found between the magnitude of reduction and the degree of similarity between the orthographic structures of the two written languages. It is concluded that reading logographic and reading phonetic symbols entail different processing mechanisms and that controversial issues in bilingual processing cannot be resolved without taking into account the effect of orthographic variations on the information processing system.     

Memory for two types of spatial location: effects of instructions, age, and format

Three experiments, with old persons (59-80 years) and college students (17-30 years) in Experiments 1 and 2 and with college students (17-24 years) in Experiment 3, investigated the differences between two types of spatial location memory: memory for the location of individual items in an array and memory for occupied, as opposed to unoccupied, locations in an array. Young persons performed better than old persons on both measures of location memory. However, an effect of instructions (intentional vs. incidental for spatial location) was consistently obtained for memory for occupied, as opposed to unoccupied, locations, whereas no effect of instructions was obtained for memory for individual item locations. In addition, item location memory was superior for objects as opposed to matched words (Experiment 2), whereas occupied location memory was not affected by presentation format (Experiments 2 and 3). These differences indicate that spatial memory is a complex process whose properties are affected by variations in stimulus characteristics and task demands. It was concluded that the distinction of Hasher and Zacks (1979) between automatic and effortful processes is not adequate for understanding spatial memory. A recognition of the complex nature of spatial processing suggests a resolution of discrepancies in the literature based upon differences in stimulus characteristics, task demands, and the effectiveness of task-appropriate mnemonic strategies.     

Examining the effects of postural constraints on estimating reach

The tendency to overestimate has consistently been reported in studies of reachability estimation. According to one of the more prominent explanations, the postural stability hypothesis, the perceived reaching limit depends on the individual's perceived postural constraints. To test that proposition, the authors compared estimates of reachability of 38 adults (a) in the seated posture (P1) and (b) in the more demanding posture of standing on one foot and leaning forward (P2). Although there was no difference between conditions for total error, results for the distribution and direction of error indicated that participants overestimated in the P1 condition and underestimated in the P2 condition. It therefore appears that perceived postural constraints could be a factor in judgments of reachability. When participants in the present study perceived greater postural demands, they may have elected to program a more conservative strategy that resulted in underestimation.     

A note on alternative parameterizations of a model for evaluating agreement between two tests

The agreement between two competing tests which purport to measure the same trait is a common concern in test development. In this paper three alternative parameterizations of the measurement model useful in this context are presented. Both one‐factor and two‐factor approaches are applied. Lord's classic example, where the main problem is to investigate whether time limits represent an extra speed component in a vocabulary test, is used to illustrate the ideas.     

The biasing effects of selection and attrition on estimating the mean

Organizational and validation researchers often work with data that has been subjected to selection on the predictor and attrition on the criterion. These researchers often use the data observed under these conditions to estimate either the predictor or criterion's restricted population means. We show that the restricted means due to direct or indirect selection are a function of the population means plus the selection ratios. Thus, any difference between selected mean groups reflects the population difference plus the selection ratio difference. When there is also attrition on the criterion, the estimation of group differences becomes even more complicated. The effect of selection and attrition induces measurement bias when estimating the restricted population mean of either the predictor or criterion. A sample mean observed under selection and attrition does not estimate either the population mean or the restricted population mean. We propose several procedures under normality that yield unbiased estimates of the mean. The procedures focus on correcting the effects of selection and attrition. Each procedure was evaluated with a Monte Carlo simulation to ascertain its strengths and weaknesses. Given appropriate sample size and conditions, we show that these procedures yield unbiased estimators of the restricted and unrestricted population means for both predictor and criterion. We also show how our findings have implications for replicating selected group differences.     

Internet-based treatment of social phobia: a randomized controlled trial comparing unguided with two types of guided self-help

Internet-based self-help for social phobia with minimal therapist support via email have shown efficacy in several controlled trials by independent research teams. The role and necessity of therapist guidance is, however, still largely unclear. The present study compared the benefits of a 10-week web-based unguided self-help treatment for social phobia with the same intervention complemented with minimal, although weekly, therapist support via email. Further, a third treatment arm was included, in which the level of support was flexibly stepped up, from no support to email or telephone contact, on demand of the participants. Eighty-one individuals meeting diagnostic criteria for social phobia were randomly assigned to one of the three conditions. Primary outcome measures were self-report measures of symptoms of social phobia. Secondary outcome measures included symptoms of depression, interpersonal problems, and general symptomatology. Measures were taken at baseline, post-treatment, and at 6-month follow-up. Data from a telephone-administered diagnostic interview conducted at post-treatment were also included. Results showed significant symptom reductions in all three treatment groups with large effect sizes for primary social phobia measures (Cohen’s d = 1.47) and for secondary outcome measures (d = 1.16). No substantial and significant between-groups effects were found on any of the measures (Cohen’s d = 00–.36). Moreover, no difference between the three conditions was found regarding diagnosis-free status, clinically significant change, dropout rates, or adherence measures such as lessons or exercises completed. These findings indicate that Internet-delivered treatment for social phobia is a promising treatment option, whether no support is provided or with two different types of therapist guidance.