Editing Longitudinal study (section)

== Advantages ==
When longitudinal studies are [[observational study|observational]], in the sense that they observe the state of the world without manipulating it, it has been argued that they may have less power to detect [[causality|causal relationships]] than [[experiment]]s. Others say that because of the repeated observation at the individual level, they have more power than cross-sectional observational studies, by virtue of being able to exclude time-invariant unobserved individual differences and also of observing the temporal order of events.<ref>{{cite journal |last1=van der Krieke |first1=Lian |last2=Blaauw |first2=Frank J. |last3=Emerencia |first3=Ando C. |last4=Schenk |first4=Hendrika M. |last5=Slaets |first5=Joris P.J. |last6=Bos |first6=Elisabeth H. |last7=de Jonge |first7=Peter |last8=Jeronimus |first8=Bertus F. |date=August 2016 |title=Temporal Dynamics of Health and Well-Being: A Crowdsourcing Approach to Momentary Assessments and Automated Generation of Personalized Feedback |journal=[[Psychosomatic Medicine (journal)|Psychosomatic Medicine]] |location=Philadelphia, Pennsylvania |publisher=[[Lippincott Williams & Wilkins]] |volume=79 |issue=2 |pages=213–223 |doi=10.1097/PSY.0000000000000378 |pmid=27551988 |s2cid=10955232|url=https://pure.rug.nl/ws/files/40193705/00006842_201702000_00011.pdf }}</ref>{{Failed verification|date=August 2020|reason=looked at article and can't seem to find this language and not clearly a good source for such information}}

Longitudinal studies do not require large numbers of participants (as in the examples below). Qualitative longitudinal studies may include only a handful of participants,<ref>{{cite journal |last1=Wood |first1=Jennifer P. |last2=Connelly |first2=Denise M. |last3=Maly |first3=Monica R. |date=November 2010 |title='Getting back to real living': A qualitative study of the process of community reintegration after stroke |journal=[[Clinical Rehabilitation]] |location=Thousand Oaks, California |publisher=[[SAGE Publications]] |volume=24 |issue=11 |pages=1045–56 |doi=10.1177/0269215510375901 |pmid=20713436 |s2cid=40295472}}</ref> and longitudinal pilot or feasibility studies often have fewer than 100 participants.<ref>{{cite journal |last1=Freeman |first1=Joshua R. |last2=Whitcomb |first2=Brian W. |last3=Roy |first3=Amrita |last4=Bertone-Johnson |first4=Elizabeth R. |last5=Reich |first5=Nicholas G. |last6=Healy |first6=Andrew J. |date=August 2018 |title=A pilot longitudinal study of anti-Müllerian hormone levels throughout gestation in low risk pregnancy |journal=Health Science Reports |location=Hoboken, New Jersey |publisher=[[Wiley (publisher)|Wiley]] |volume=1 |issue=8 |pages=e53 |doi=10.1002/hsr2.53 |pmc=6266452 |pmid=30623089}}</ref>