In order to clarify the terminology and outline the major parameters in survey design, this section provides a brief discussion of the major design features of surveys:
• Frequency options include data collection on a continuous basis, fixed periodic basis, irregular periodic basis, one-time or ad-hoc studies. Frequency is determined by need to detect changes over time and the likelihood of change.
• Geographic detail: national, regional, State, local. Most HHS surveys are designed to provide national and regional estimates.
• Population detail: subgroups of the population are defined by their race/ethnicity, poverty status, health characteristics, disability/functional limitation, age, and other characteristics. Most surveys require some detail on a variety of population subgroups in order to provide for adequate analytic capability. In order to provide the numbers to support such analysis, most HHS surveys make concerted efforts to screen and oversample population subgroups of interest. The groups oversampled vary by the objectives of the survey; for example, high expenditure groups are targeted by NMES; the young, race/ethnic minorities, and cigarette smokers are targeted by the National Household Survey on Drug Abuse; and race/ethnic minorities are oversampled in the National Health Interview Survey.
• Data sources: respondents to interview surveys include individuals, parents, family members or other proxy respondents, employers, and in some cases health care providers. Other surveys rely on administrative records maintained by health providers or employers. In some cases, providers are enlisted to record information about their encounters with individual patients.
• Mode of data collection: methods include household (in-person) interviews, telephone interviews (either RDD - random digit dialed, list-assisted, or calls made to known persons); self-administered questionnaires; direct physical and laboratory measurement; or abstracting of information from records. Each of these modes can be assisted by automated techniques, including Computer Assisted Personal Interview (CAPI), which uses laptop interviews in household interviews; Computer Assisted Telephone Interviews (CATI); Computer Assisted Self Interviewing, in which respondents interact directly with the CAPI system; and electronic access to provider records.
• Survey content. Depending on analytic needs and operational constraints, surveys range from highly detailed (such as NMES expenditure questionnaire and NHANES laboratory measurements) to more abridged or summary questionnaires.
• Data Quality, as measured by validity and reliability.
• Timeliness of data, both in terms of the length of time needed to obtain data (e.g., multiple visits over a year to the same individual, or surveying different individuals over a period of years to obtain sufficient sample size) as well as time needed to process data.
• Analytic uses, which include descriptive statistics, multivariate analysis, predictive modeling, and microsimulation.