Paul Stapleton's (2006) critique of quantitative research brings to the surface some common interpretive problems arising when experimental and quasi-experimental research designs are compared. While Stapleton may be correct in pointing out the superiority of experimental research designs because they best eliminate the influence of extraneous…

Modeling the process by which participants are selected into groups, rather than adjusting for preexisting group differences, provides the basis for several new approaches to the analysis of data from nonrandomized studies. Econometric approaches, the propensity scores approach, and the relative assignment variable approach to the modeling of…

Causal models often omit variables that should be included, use variables that are measured fallibly, and ignore time lags. Such practices can lead to severely biased estimates of effects. The discussion explains these biases and shows how to take them into account. (Author)

This paper comments on strengths and weaknesses of the papers on communities of practice in this special issue of "Technology, Pedagogy and Education." First it discusses the character of communities of practice and the question of whether schools are environments that are conducive to the development of teacher communities of practice. It then…