What is the field that will be covered by a particular procedure? Consider the following aspects.
What set of events or individuals will be examined?
For example, will the statistical work focus on children or will it include persons of all ages?
What geographical area will be covered?
For example, will the estimate pertain to one particular city or state or does the data collector need to generalize National conditions?
Will the results support comparative estimates for states, cities, metropolitan areas or rural areas?
Decisions about the geographic scope of data collection depend on the requirement for local estimates as well as assumptions about the homogeneity of a condition or procedure.
For example, sometimes researchers use information collected in a limited set of places as indicative of national conditions because they do not believe that there is important geographic variation that would change their conclusions.