Single Case, Quasi-Experimental, and Developmental Research

Single Case, Quasi-Experimental, and Developmental Research

1. Describe single case experimental designs and discuss reasons to use this design

   • Single case experiments were developed from a need to determine whether an experimental manipulation had an effect on a single research participant. Often seen in clinical, counselling, educational, and other applied settings. In a single case design, the subject's behavior is measured over time during a baseline control period.

2. Describe the five types of evaluations involved in program evaluation research: needs assessment, program assesssment, process evaluation, outcome evaluation, and efficiency assessment

   • Program evaluation is research on programs that are proposed and implemented to achieve some positive effect on a group of individuals
   • Program evaluation that focuses on needs assessment asks whether there are problems that need to be addressed in a target population
   • The assessment of program theory may involve the collaboration of researchers, service providers, and prospective clients of the program to determine that the proposed program does in fact address the needs of the target population in appropriate ways
   • Process evaluation, when the program is under way, the evaluation researcher monitors it to determine whether it is reaching the target population, whether it is attracting enough clients, and whether the staff is providing the planned services
   • Outcome evaluation, are the intended outcomes of the program being realized? Is the goal being achieved?
   • Efficiency assessment, once it is shown that a program does have its intended effect, researchers must determine whether it is "worth it". The cost of the program must be weighted against its benefits

3. Describe the one-group posttest-only design

   • Lacks a crucial element of a true experiment: a control or comparison group
   • The one group posttest-only design with its missing comparison group is seriously deficient in internal validity. This is not an experiment that will allow us to draw causal inferences

4. Describe the one-group pretest-posttest design and the associated threats to internal validity that may occur: history, maturation, testing, instrument decay, and regression toward the mean

   • One way to obtain a comparison is to measure participants before the manipulation and again afterward
   • Threats to Internal Validity
     • History effects can be caused by virtually any confounding event that occurs during or after the experimental manipulation, but before the posttest
     • Maturation effects are any changes systematically over time
     • Testing effects become a problem if simply taking the pretest changes the participants behavior
     • The basic characteristics of the measuring instrument, or the way participants use it, change over time; this is called instrument decay
     • Regression toward the mean is likely to occur whenever participants are selected to participate because they score extremely high or low on some variable. When they are tested again, their scores tend to change in the direction of the mean

5. Describe the nonequivalent control group design and nonequivalent control group pretest-posttest design, and discuss the advantages of having a control group

   • Non-equivalent control group design
     • Employs a separate control group, but the participants in the two conditions - the experimental group and the control group - are not equivalent because the participants were not randomly assigned
       • Selection differences, usually occurs when participants who form the two groups in the experiment are chosen from existing natural groups
   • Non-equivalent control group pretest-posttest design
     • One of the most useful quasi-experimental designs, although it can never be as internally valid as a true experiment
       • This is not a true experiment design because assignment to groups is not random; the two groups may not be equivalent
       • We have the advantage of knowing pretest scores. Even if the groups are not equivalent, we can look at changes in scores from the pretest to the posttest. If the independent variable has an effect the experimental group should show a greater change than the control group.

6. Distinguish between the interrupted time series design and control series design

   • Interrupted time series design
     • Looking at years before and after the implementation of a new program
   • Control series design
     • One way to improve the interrupted time series design is to find some kind of control group

7. Describe cross-sectional, longitudinal, and sequential research designs, including the advantages and disadvantages of each design

   • Longitudinal Method
     • The same group of people is observed at different points in time as they grow older
     • Despite being expensive and difficult, it has definite advantages. One major problem: Over, the course of a longitudinal study, people may move, die, or lose interest in the study. There is a great risk of a high participant mortality rate
   • Cross-sectional Method
     • Persons of different ages are studied at only one point in time
     • Much more common than the longitudinal method, primary because it is less expensive and immediately yields useful results
   • Sequential Method
     • A compromise between the longitudinal and cross-sectional methods
     • The first phase of the sequential method begins with the cross sectional method. These individuals are then studied using the longitudinal method with each individual tested at least one more time. This method takes fewer years to complete than a longitudinal study, and the researcher reaps immediate rewards because data of the different groups are available in the first year of the study

8. Define cohort effect

   • In a cross-sectional study, difference among groups of different ages may reflect developmental age changes