The next step, the research design, addresses how to implement the strategy.
Determining a research design requires decisions about three basic aspects of
the research study:
1. Group versus individual. Will the study examine a group of individuals,
producing an overall description for the entire group, or should the study focus on a single individual? Although group studies tend to have
higher external validity (results from a large group can be more confidently
generalized than results from a single individual), the careful
examination of a single individual often can provide detail that is lost in
averaging a large group.
2. Same individuals versus different individuals. Some research examines
changes within the same group of individuals as they move from one
treatment to the next. Other research uses a different group of individuals
for each separate treatment and then examines differences between
groups. Each design has advantages and disadvantages that must be
weighed in the planning phase.
3. The number of variables to be included. The simplest study involves
examining the relationship between two variables. However, some
research involves three or more variables. For example, a researcher may
be interested in multiple relationships, or a study may focus on two
variables but ask how their relationship is affected by other variables.
Thus, one factor in determining a research design is deciding how many
variables will be observed, manipulated, or regulated.