Theoretical models specifying indirect or mediated effects are common in the social sciences. An indirect effect exists when an independent variable's influence on the dependent variable is mediated through an intervening variable. Classic approaches to assessing such mediational hypotheses (Baron & Kenny, 1986; Sobel, 1982) have in recent years…

A latent variable analysis procedure for evaluation of reliability coefficients for 2-level models is outlined. The method provides point and interval estimates of group means' reliability, overall reliability of means, and conditional reliability. In addition, the approach can be used to test simple hypotheses about these parameters. The…

Most of the statistical procedures in meta-analysis are based on the estimation of average effect sizes from a set of primary studies. The optimal weight for averaging a set of independent effect sizes is the inverse variance of each effect size, but in practice these weights have to be estimated, being affected by sampling error. When assuming a…

This article provides a conceptual introduction to the issues surrounding the analysis of clustered (nested) data. We define the intraclass correlation coefficient (ICC) and the design effect, and we explain their effect on the standard error. When the ICC is greater than 0, then the design effect is greater than 1. In such a scenario, the…

Imagery training has been shown to improve reading comprehension. Recent research has also shown that the quality of visual mental imagery used is important for reading comprehension. A review of literature shows that there has been relatively little detailed research on the quality of imagery used by learners, especially in the case of students…

Theory-driven conceptualizations of phonological abilities in a sufficiently transparent language (Greek) were examined in children ages 5 years 8 months to 7 years 7 months, by comparing a set of a priori models. Specifically, the fit of 9 different models was evaluated, as defined by the Number of Factors (1 to 3; represented by rhymes,…

Statistical modeling of school effectiveness data was originally motivated by the dissatisfaction with the analysis of (school-leaving) examination results that took no account of the background of the students or regarded each school as an isolated unit of analysis. The application of multilevel analysis was generally regarded as a breakthrough,…

Quantum mechanics is often thought to be a difficult subject to understand, not only in the complexity of its mathematics but also in its conceptual foundation. In this paper we emphasize students' depictions of the uncertainty principle and wave-particle duality of quantum events, phenomena that could serve as a foundation in building an…

Non-exercise equations developed from self-reported physical activity can estimate maximal oxygen uptake (VO[subscript 2]max) as well as sub-maximal exercise testing. The International Physical Activity Questionnaire is the most widely used and validated self-report measure of physical activity. This study aimed to develop and test a VO[subscript…

To realize the benefits of item response theory (IRT), one must have model-data fit. One facet of a model-data fit investigation involves assessing the tenability of the conditional item independence (CII) assumption. In this Monte Carlo study, the comparative performance of 10 indices for identifying conditional item dependence is assessed. The…

ABILHAND is, in its original version, a 46-item, 4-level questionnaire. It measures the difficulty perceived by patients with rheumatoid arthritis as they do various daily manual tasks. ABILHAND was originally built through Rasch analysis. In a later study, it was simplified to a generic 23-item, three-level questionnaire, showing both…

A new form of composition of the indicators employed to generate the United Nations Human Development Index (HDI) is presented here. This form of composition is based on the assumption that random errors affect the measurement of each indicator. This assumption allows for replacing the vector of evaluations according to each indicator by vectors…

In this study the psychometric properties of the Trunk Control Measurement Scale (TCMS) in children with cerebral palsy (CP) were examined. Twenty-six children with spastic CP (mean age 11 years 3 months, range 8-15 years; Gross Motor Function Classification System level I n = 11, level II n = 5, level III n = 10) were included in this study. To…

The assessment of positive affect (PA) and negative affect (NA) by means of the Positive Affect and Negative Affect Schedule has received a remarkable popularity in the social sciences. Using a meta-analytic tool--namely, reliability generalization (RG)--population reliability scores of both scales have been investigated on the basis of a random…

As the United States becomes more racially and ethnically diverse and draws more students from across the globe, more representative data are needed to understand at-risk and underrepresented populations in higher education, particularly in the science, technology, engineering, and mathematics (STEM) fields. The authors argue that the current…