What do the values in time method mean?

  • Longitudinal - Data collected repeatedly over time to study change in a population.
  • Longitudinal:Cohort/Event-based - Data collected over time about a group of individuals that are connected in some way or have shared some significant experience within a given period. Examples: birth, disease, education, employment, family formation.
  • Longitudinal:Trend/Repeated Cross-section - Studies different samples /groups of people from the same population at several points in time; conclusions are drawn for the population. Examples: public opinion polls, elections studies, etc.
  • Longitudinal:Panel - Data collected over time from, or about, the same sample of respondents.
  • Longitudinal:Panel:Continuous - Reports from the panel are collected on a regular basis.
  • Longitudinal:Panel:Interval - Measurements are taken only when information is needed.
  • Time Series - Data are collected repeatedly over time to study change in observations.
  • Time Series:Continuous - Phenomena are measured at every instant of time. Examples: lie detectors, electrocardiograms, etc.
  • Time Series:Discrete - Measurements are taken at (usually regularly) spaced intervals. Examples: macroeconomics (weekly share prices, monthly profits, sales, etc.), meteorology (daily rainfall, hourly temperature, etc.), sociology (crime figures, employment figures, etc.).
  • Cross-sectional - Data about a population are obtained only once.
  • Cross-sectional ad-hoc follow-up - Data collected at one point in time to complete information collected in a previous cross-sectional study; the decision to collect follow-up data is not included in the study design.

Please note that ICPSR has not yet retroactively applied the time method field to all 8000+ studies we archive.