Randomized experiments are often seen as the "gold standard" for causal research. Despite the fact that experiments use random assignment to treatment conditions, units are seldom selected into the experiment using probability sampling. Very little research on experimental design has focused on how to make generalizations to well-defined…

The Penn Manor CRT/Curriculum Articulation Project was designed to study the impact of the implementation of four specific interventions on the achievement of elementary school students in mathematics and language arts. The interventions were as follows: (1) classroom teachers were given individual curriculum skill objectives for their grade…