Introduction to Research Design

Introduction to Research Design

What Is Research Design? The structure of research

Elements of a Design • Observations or measures • Treatments or programs • Groups • Assignment to group • 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 R O X O R O O

Design Notation Example R O X O R O O Time

Design Notation Example R O X O R O O Os indicate different waves of measurement.

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

Design Notation Example X is the treatment. R O X O R O O

Design Notation Example There are two lines, one for each group. R O X O R O O

Design Notation Example R O X O R O O R indicates the groups are randomly assigned.

Design Notation Example R O1 X O1, 2 R O1 O1, 2 Subscripts indicate subsets of measures.

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

Introduction to Research Design