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 some randomized clinical trials, patients may die before the measurements of their outcomes. Even though randomization generates comparable treatment and control groups, the remaining survivors often differ significantly in background variables that are prognostic to the outcomes. This is called the truncation by death problem. Under the…

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…

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).…

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…