I. Single group Designs
This might be the case of experimental treatments of that have a high degree of risk, and only one or a few "patients" or subjects may be examined with the new (medical) treatment. These are called single-subject or single participant designs.
The most commonly used style of these are the "Baseline" studies where pre- and post- functioning are examined.
Another method to test the efficacy of such treatments is also to use the "Reversal Designs" where the treatment is given then taken away to see if the effect diminishes. Here one makes use of the A-B-A style of where A is the baseline and B is the treatment.
As Cozby points out it might be unethical to remove the treatment (if there is an effect) then the ABAB design is used to reestablish the treatment after examining the effect of having removed it.
Interrupted Time Series
Another Specialized type of design is the Interrupted time series design where archival records may be examined be and after an intervention or manipulation such as changing the penalties for drinking and driving or speeding. Here rates of car crashes may be used to examine the efficacy of the reformed laws.
Multiple Base-line designs may also be used where it is unethical or impractical to do reversal designs.
Here the treatment is given to participants at different times through the study. This should show the efficacy of the treatment under different circumstances, and it can be done across subjects or across behaviours.
Across subjects looks at the treatment (i.e., relaxation therapy) across various subjects getting it at different times as indicated in Figure 11.2 (p.204).
The across behaviours design will apply the treatment (behavioural technique) to the same participant(s) to different behaviours.
III. Program Evaluation
Program Evaluation is another important application of research design that may use experimental, but is more likely to use quasi-experimental designs (i.e., the efficacy of changing vending machine contents).
There are a number of aspects or stages of program evaluation that may be considered.
Needs Assessment - involves the examination of a community or individual's needs and whether or not they are being met.
Program Theory Assessment - involves the evaluation of a theory as applied to a specific program, testing its efficacy.
Process of Evaluation - examines the implementation of a program and whether or not it meets the specific needs that were assessed.
Outcome Evaluation - evaluates the impact of the program and seeks to establish impact assessment.
Efficiency Evaluation - examines the overall program and what may need to be changed or altered to meet the original needs and process and outcomes.
The Sequential Model is a compromise between cross-sectional and Longitudinal studies where one starts off with a cross-section of ages and then follows up (at least the younger group) as they ages over a shorter period of time.