There has been considerable recent interest in methods of determining sample size for qualitative research a priori, rather than through an adaptive approach such as saturation. Extending previous literature in this area, we identify four distinct approaches to determining sample size in this way: rules of thumb, conceptual models, numerical…

As research on mediation has grown, so too has interest in identifying ways to assess the size of indirect effects in a mediation analysis. One such estimate -- the ratio of the indirect effect to the total effect (P[subscript M]) -- was tested in a sample of 21,297 children from the Early Childhood Developmental Study. Results showed that the two…

Humans possess an invaluable ability of self-expression that extends into visual, literary, musical, and many other fields of creation. More than any other profession, artists are in close contact with this subdomain of creativity. Probably one of the most intriguing aspects of creativity is its negative correlation with the availability of…

Propensity and prognostic score methods are two statistical techniques used to correct for the selection bias in nonexperimental studies. Recently, the joint use of propensity and prognostic scores (i.e., two-score methods) has been proposed to improve the performance of adjustments using propensity or prognostic scores alone for bias reduction.…

School principals are tasked with a daunting number of responsibilities, all of which must culminate in increased student achievement. The complexity of these responsibilities have left school leaders overwhelmed, resulting in diminished confidence and potentially substandard job performance. This study addressed the problem that many school…

The present study examined the activation of imaginal information on true and false memories. We asked whether forming mental images would lead to increases in true and false memories relative to a control group that did not form images. Participants in both groups studied 288 unrelated concrete objects, in which some of the objects were presented…

This comment discusses some issues about the use and reporting of experimental studies in education, illustrated by a recently published study that claimed (i) that an educational innovation was effective despite outcomes not reaching statistical significance, and (ii) that this refuted the findings of an earlier study. The two key issues raised…

The hierarchical model of van der Linden is the most popular model for responses and response times in tests. It is composed of two separate submodels--one for the responses and one for the response times--that are joined at a higher level. The submodel for the response times is based on the lognormal distribution. The lognormal distribution is a…

In large-scale low-stake assessment such as the Programme for International Student Assessment (PISA), students may skip items (missingness) which are within their ability to complete. The detection and taking care of these noneffortful responses, as a measure of test-taking motivation, is an important issue in modern psychometric models.…

Estimating the effects of randomized experiments and, by extension, their mediating mechanisms, is often complicated by treatment noncompliance. Two estimation methods for causal mediation in the presence of noncompliance have recently been proposed, the instrumental variable method (IV-mediate) and maximum likelihood method (ML-mediate). However,…

Properties of psychological variables at the mean or variance level can differ between persons and within persons across multiple time points. For example, cross-sectional findings between persons of different ages do not necessarily reflect the development of a single person over time. Recently, there has been an increased interest in the…

The process of quantification is a powerful development shaping many domains of life today. In the area of education, for example, performance measurement, testing and ranking have become common tools of governance. Quantification is not a neutral way of describing society, but a process of valorisation. It has three sociologically relevant…

This article contends that the 'go-along' contains more technical and ontological agility as a methodology for social research than is often assumed. After distinguishing the central spectrums of technical and ontological agility rooted in different research designs and philosophical orientations, I examine how researchers can nourish it while…

Preschool period covers the years when the child is in a rapid change and development in every aspect. The learning experiences in this period affect children's development. The developments in knowledge technologies affect the child's environment and children's books. This rapid change brings with it some discussions. "Do either traditional…

We derive sample-allocation formulas that maximize the power of several mediation tests in two-level-group-randomized studies under a linear cost structure and fixed budget. The results suggest that the optimal individual sample size is typically smaller than that associated with the detection of a main effect and is frequently less than 10 under…