single subject experimental design
Definition
Single-subject design: A type of quasi-experimental research design using one subject to test all treatment and control conditions over time (e.g., an ABAB design).
Notes
Single-subject designs also uncover cause-and-effect relationships by involving an intervention, but they use unique control procedures and involve different types of evidence to support those relationships. (Suter 2012, pg. 3)
Single-subject quasi-experimental designs (e.g., multiple baseline) establish control and evaluate treatment effects by alternating baseline and treatment conditions while observing patterns over time and across conditions. (Suter 2012, pg. 35)
Also called single-case designs, single-subject designs involve studying the effect of a treatment on a single subject (or a single group, such as an entire classroom) in an adaptation of a time series design. They are considered “experimental” because they involve the introduction of a treatment of some sort and accomplish their control through the use of comparisons between baseline observations and treatment observations. These designs, then, involve observing behavior over a period of time as a function of baseline and treatment conditions in an effort to establish casual relations.
They often involve several phases, such as the withdrawal of treatment followed by its introduction in a reverse manner. Baseline performance, or the absence of treatment, is often labeled A and compared with treatment performance, which is often labeled B. These designs, in fact, are typically referred to as ABAB, BAAB, ABA, or some other configuration showing how the baseline and treatment conditions are alternated or staggered.
Single-subject quasi-experimental designs (e.g., multiple baseline) establish control and evaluate treatment effects by alternating baseline and treatment conditions while observing patterns over time and across conditions. Can you think of instances where single-subject designs are especially well suited to education? In what situations may such designs be inappropriate? (pg. 35)