Causal effects are commonly defined as comparisons of the potential outcomes under treatment and control, but this definition is threatened by the possibility that either the treatment or the control condition is not well defined, existing instead in more than one version. This is often a real possibility in nonexperimental or observational…

In experimental research, internal validity refers to what extent researchers can conclude that changes in dependent variable (i.e. outcome) are caused by manipulations in independent variable. The causal inference permits researchers to meaningfully interpret research results. This article discusses (a) internal validity threats in social and…

There are few high-quality studies using randomized controlled trials (RCTs) in the adventure and wilderness therapy literature. Thus, a unison call is heard for more such studies to be carried out. This article presents a Norwegian wilderness therapy research project that planned to incorporate this "gold standard" that is regarded as…

Meta-analyses are syntheses of effect-size estimates obtained from a collection of studies to summarize a particular field or topic (Hedges, 1992; Lipsey & Wilson, 2001). These reviews are used to integrate knowledge that can inform both scientific inquiry and public policy, therefore it is important to ensure that the estimates of the effect…

Randomized controlled trials (RCTs) and regression discontinuity (RD) studies both provide estimates of causal effects. A major difference between the two is that RD only estimates local average treatment effects (LATE) near the cutoff point of the forcing variable. This has been cited as a drawback to RD designs (Cook & Wong, 2008).…

Organizational and applied sciences have long struggled with improving causal inference in quasi-experiments. We introduce organizational researchers to propensity scoring, a statistical technique that has become popular in other applied sciences as a means for improving internal validity. Propensity scoring statistically models how individuals in…

As a result of the 1998 reauthorization of Head Start, the Department of Health and Human Services conducted a national evaluation of the Head Start program. The goal of Head Start is to improve the school readiness skills of low-income children in the United States. There is a substantial body of experimental and correlational research that has…

Introduction: A correspondence has been seen between the level at which one can read scientific texts and his/her performance in writing this type of texts. Besides being able to read at the most complex levels, formulating research problems requires explicit training in writing. The objective of the present study was to evaluate whether…

This paper introduces an empirical strategy to estimate dynamic treatment effects in randomized trials that provide treatment in multiple stages and in which various noncompliance problems arise such as attrition and selective transitions between treatment and control groups. Our approach is applied to the highly influential four year randomized…

Recognition of radio and television antismoking messages was measured in 6 treatment and 4 control cities. A survey of 574 adolescents found high recognition of messages even in areas where they were not broadcast, reinforcing the need for true control groups and distinctive messages to ensure validity in mass media evaluation. (SK)

An evaluation of one therapeutic service offered to sexually abused children in the United Kingdom exposed the methodological issue of false negatives among the comparison group, suggesting that researchers cannot assume that nonreferred comparison subjects have not actually experienced sexual abuse. (DB)

In a nonrandomized or observational study, propensity scores may be used to balance observed covariates and trajectory groups may be used to control baseline or pretreatment measures of outcome. The trajectory groups also aid in characterizing classes of subjects for whom no good matches are available and to define substantively interesting groups…

A persistent problem in the evaluation of field-based projects is the lack of no-treatment comparison groups. Frequently, potential comparison groups are confounded by socioeconomic, racial, or other factors. Among the possible methods for dealing with this problem are various matching procedures, but they are cumbersome to use with multiple…

A relationship between experimental and statistical controls is considered in an effort to show how this relationship affects the power of an experiment. Statistical rather than experimental controls are often used to reduce the effect of subjects at the extremes of individual difference. This results in attrition of actual experimental subjects.…

Eighty preschoolers participated in a study of the usefulness of the lure-retrieval paradigm. Four treatment conditions were compared: In addition to play and training conditions, a questions condition and an alternative-materials control group were employed. Results prompted discussion of theoretical and methodological issues surrounding the…