Introduction to Research Design

What Is Research Design? The structure of research

Elements of a Design l Observations or measures l Treatments or programs l Groups l Assignment to group l Time

Observations or Measures Symbolized with an "O". Subscripts are used to distinguish different combinations of measures only if this is necessary.

Treatments or Programs Symbolized with an "X". Subscripts are used to indicate different programs or combinations of programs.

Groups Each group of interest on its own line.

Assignment to Groups R = Random assignment N = Nonequivalent groups C = Assignment by cutoff

Time Left-to-right movement denotes the passage of time.

Design Notation Example ROXOROOROXOROO

ROXOROOROXOROO Time

ROXOROOROXOROO Os indicate different waves of measurement.

Design Notation Example ROXOROXOROOROOROXOROXOROOROO Vertical alignment of Os shows that pretest and posttest are measured at same time.

Design Notation Example ROXOROOROXOROO X is the treatment.

Design Notation Example ROXOROOROXOROO There are two lines, one for each group.

Design Notation Example ROXOROOROXOROO R indicates the groups arerandomlyassigned.

Design Notation Example RO 1 XO 1, 2 RO 1 O 1, 2 Subscriptsindicate subsets of measures.

Design Notation Example Pretest-posttest (before-after) Treatment versus comparison group Randomized experimental design= ROXOROOROXOROO