Which of the many different types of research design is best for you?
One thing that you will want to consider early in your dissertation process is the design of your research study. By the time you start your dissertation or thesis, you have probably taken graduate and undergraduate courses about research methods; however, it has probably been a while since you have taken these courses, and you may need help sorting through all the different types of research design. Below is a brief refresher on different research designs and methodologies.
General Types of Research Designs
Descriptive: Researchers use descriptive research designs to describe particular phenomena or relationships within a single group sample. Descriptive designs are typically used as either pilot or preliminary studies and generally have rather basic statistical procedures. By nature, descriptive studies do not and cannot be used to explain causation.
Descriptive research designs usually provide researchers with information about a group or phenomenon about which there has been little research (e.g., mating patterns of Martians). However, descriptive studies lack randomization and control and cannot be used to determine causation and other implications; in other words, descriptive research designs can only be used to determine “who” and “what,” not “why.”
Quasi-Experimental: Researchers use quasi-experimental research designs to identify differences between two or more groups in an attempt to explain causation. What keeps these types of experiments from being true experiments is lack of randomization. For example, researchers cannot randomly assign gender to participants; therefore, any study in which researchers are investigating differences between genders is inherently quasi-experimental.
Quasi-experimental designs allow researchers more control to make assumptions about causation and implications of findings. Quasi-experimental designs are also useful when researchers want to study particular groups in which group members cannot be randomly assigned (e.g., persons with depression, single mothers, people from different races or ethnic groups, etc.). A major drawback to using quasi-experimental designs is that quasi-experimental research designs typically have less internal validity than do true experimental designs.
Experimental: Experimental research designs have the most control, and, thus, allow researchers to explain differences between groups. One of the key features of an experimental design is that participants are randomly assigned to groups. Experimental designs can be used to test differences between groups (e.g., treatment a group, treatment b group, and control group) or factorial differences within multiple levels of each group (e.g., a drug group [Xanax or Valium] and a psychotherapy group [Cognitive Behavioral Therapy or Rational Emotive Behavioral Therapy]).
True experimental research designs are understood to be the gold standard of research because experimental research designs are the best designs for researchers to predict causation. However, true experimental designs often require more resources than do other research designs and will not work with all research questions.
Specific Types of Research Designs
Single-Sample Repeated Measures: A design method in which the same group is tested at multiple points in time. Giving students an assessment of knowledge the first day of class and giving the same assessment on the last day of class is an example of a research design based on a single-sample repeated measures.
ABA: A specific single-sample repeated measures design in which participants are measured at baseline (A), after an intervention (B), and again after the intervention has been removed (A).
Between Groups: A design in which researchers compare the scores of two or more groups. Between-group designs can be used as either a single or repeated measure.
Matched Sample: A specific between-groups design in which researchers match participants across groups based on criteria determined by the researchers (e.g., age, IQ, gender, etc.). After matching participants based on the predetermined criteria, researchers examine differences between matched pairs (not between group means).