Σύγκριση μεθόδων

	Τεχνική Delphi	Διαχρονική Έρευνα	Διαδικτυακή Έρευνα
Πεδίο	Μεθοδολογία Επισκοπήσεων	Μεθοδολογία Επισκοπήσεων	Μεθοδολογία Επισκοπήσεων
Οικογένεια	Process / pipeline	Process / pipeline	Process / pipeline
Έτος προέλευσης	1950s–1963	1940s (panel survey tradition); longitudinal designs codified mid-20th century	Mid-1990s (widespread scholarly adoption ~1995–2000)
Δημιουργός	Norman Dalkey and Olaf Helmer (RAND Corporation)	Established tradition; formalized in social science by Paul Lazarsfeld and colleagues (1940s panel studies)	Mick P. Couper, Don A. Dillman (early systematic frameworks)
Τύπος	Iterative expert consensus technique	Quantitative / mixed-methods survey design	Quantitative / mixed-methods data collection technique
Θεμελιώδης πηγή	Dalkey, N., & Helmer, O. (1963). An experimental application of the Delphi method to the use of experts. Management Science, 9(3), 458–467.	Menard, S. (2002). Longitudinal Research (2nd ed.). Sage Publications. ISBN: 978-0761922292	Couper, M. P. (2000). Web surveys: A review of issues and approaches. Public Opinion Quarterly, 64(4), 464–494.
Εναλλακτικές ονομασίες	Delphi method, Delphi survey, expert consensus method, iterative expert panel	panel survey, repeated-measures survey, longitudinal panel study, wave survey	web survey, internet survey, e-survey, computer-assisted web interviewing
Συναφείς	6	3	6
Σύνοψη	The Delphi technique is a structured, multi-round data collection method that harvests and refines expert opinion through iterative questionnaires and controlled feedback. Developed at RAND Corporation in the 1950s, it is designed to converge a dispersed expert panel toward a reliable consensus on complex, uncertain, or future-oriented questions — without the conformity pressures of face-to-face group discussion.	A longitudinal survey collects structured questionnaire data from the same individuals or units at two or more distinct points in time. By tracking the same respondents across waves, researchers can distinguish genuine change from stable individual differences, establish temporal ordering between variables, and model trajectories of attitudes, behaviors, or outcomes in ways that a single cross-sectional snapshot cannot support.	An online survey is a structured data collection instrument hosted on a web platform and completed by respondents via internet-connected devices. It enables large-scale, geographically dispersed data gathering at low cost and with rapid turnaround. Respondents self-administer the questionnaire at their convenience, which reduces interviewer bias and permits automatic data capture. Online surveys are the dominant mode of survey research in social, behavioural, health, and market research today.