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	Longitudinal In-depth Interview	Longitudinal Survey
Ämnesområde	Surveymetodik	Surveymetodik
Familj	Process / pipeline	Process / pipeline
Ursprungsår	1990s–2000s (as a formalised qualitative method)	1940s (panel survey tradition); longitudinal designs codified mid-20th century
Upphovsperson	Rooted in qualitative longitudinal research traditions; systematised by Johnny Saldana	Established tradition; formalized in social science by Paul Lazarsfeld and colleagues (1940s panel studies)
Typ	Qualitative longitudinal data collection technique	Quantitative / mixed-methods survey design
Ursprungskälla	Saldana, J. (2003). Longitudinal Qualitative Research: Analyzing Change Through Time. AltaMira Press. ISBN: 978-0759103917	Menard, S. (2002). Longitudinal Research (2nd ed.). Sage Publications. ISBN: 978-0761922292
Alias	repeated in-depth interview, longitudinal qualitative interview, panel qualitative interview, longitudinal IDI	panel survey, repeated-measures survey, longitudinal panel study, wave survey
Närliggande	5	3
Sammanfattning	Longitudinal in-depth interviewing is a qualitative data collection technique in which the same participants are interviewed in depth on multiple occasions across a defined time span. By revisiting the same people over weeks, months, or years, researchers can trace how experiences, identities, attitudes, and meanings change — something a single interview cannot reveal. It is widely used in life-course research, health studies, education, and social policy.	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.