Completeness of Data Completeness refers to the depth and breadth of the data. Having complete data allows the researcher to paint a total picture, fully describing the information from each respondent. Incomplete data will lack some amount of detail, resulting in a picture that is somewhat vague or unclear. Personal interviews and Internet surveys tend to be complete, while mail surveys may not be. In some cases, the depth of information needed to make an informed decision will dictate that a personal survey is the appropriate method.
Data Generalizability Data that are generalizable accurately represent the population being studied and can be accurately projected to the target population. Data collected from mail surveys are frequently less generalizable than those collected from phone interviews or personal interviews due to low response rates. Small sample size will limit the generalizability of data collected using any technique. Generalizability often is a problem with online surveys as well.