S

ocial work research has become increasingly reliant on large second-

ary data sets. These data sets, generally collected by governments,

research institutions, and, in some cases, agencies, provide researchers

with readily available resources to examine characteristics of populations

or particular hypotheses. These data differ from primary data in that

primary data sets are collected by the researcher who will also examine

that data. Researchers collect primary data directly through interviews,

questionnaires, focus groups, observation, the examination of primary

sources such as writings or speeches, or a variety of other such collection

methods. While collecting data is often the best way to obtain the infor-

mation necessary to analyze particular hypotheses, it is not always eco-

nomically or practically feasible. Using large secondary data sets provides

an alternative to the collection of primary data, often giving the researcher

access to more information than would be available in primary data sets.

Secondary data can include any data that are examined to answer a

research question other than the question(s) for which the data were ini-

tially collected. Large institutions are able to obtain far larger samples

and often are able to ask more questions than researchers who are in

smaller settings (such as individual or small-group researchers). Over

time, data sets have become richer, as researchers refi ne the types of

questions asked in surveys.