Research design can be thought of as the structure of research it is the glue that holds all of the elements in a research project together. We often describe a design using a concise notation that enables us to summarize a complex design structure efficiently. The elements that a design includes are:-
1.Observations or Measures:-
These are symbolized by an o in design notation . An o can refer to a single measure a single instrument with multiple items , a complex multi-part instrument , or a whole battery of tests or measures given out on one occasion. If you need to distinguish among specific measures, you can use subscripts with the o, as in o1, o2, and so on.
2.Treatments or Programs:-
These are symbolized with an x in design notations. The x can refer to a simple intervention or to a complex hodgepodge program . Usually, a no- treatment control or comparison group has no symbol for the treatment. As with observations, you can use subscripts to distinguish different programs or program variations.
3. Groups:-
Each group in a design is given its own line in the design structure , if the design notation has three lines, there are three groups in the design.
4.Assignment to Group:-
Assignment to group is designated by a letter at the begninning of each line that describes how the group was assigned.
The major types of assignment are:
R=random assignment
N=nonequivalent groups
C=assignment by cutoff
Time time moves from left to right. Elements that are listed on the left occur before elements that are listed on the right.
Design Notation Examples-
Its always easier to explain design notation through examples than it is to describe it in words. The figure shows the design notation for a pretest - posttest treatment versus comparison group randomized experimental design each of the parts. There are two lines in the notation, so you should realize that the study has two groups. There are four os in the notation, two on each line and two for each group. When the os are stacked vertically on top of other it means they are collected at the same time. In the notation you can see that we have two os that are taken before any treatment is given - the pretest - and two os taken after the treatment is given - the posttest. The R at the beginning of each line signifies that the two groups are randomly assigned . The design is a treatment versus comparison group one because the top line has an x while the bottom line does not. You should be able to see why many of my students have called this type of notation the tic - tac - toe method of design notation - there are lots of xs and sometimes we have to be more specific in describing the os or xs than just using a single letter. In the second figure, we have the identical research design with some subscripting of the os. What does this means?
Because all of the os have a subscript of 1 there is some measure or set of measures that is collected for both groups on both occasions. But the design also has two os with a subscript of 2 both taken at the posttest. This means that there was some measure or set of measures that were collected only at the posttest.
With this simple set of rules for describing a research design in notational form, you can concisely explain even complex design structures. And , using a notation helps to show common design sub - structures across different designs that we might not recognize as easily without the notation.
