Testing for undetected withdrawal in a follow-up study of times to events

Caroni, C

dc.contributor.author	Caroni, C	en
dc.date.accessioned	2014-03-01T01:37:13Z
dc.date.available	2014-03-01T01:37:13Z
dc.date.issued	2011	en
dc.identifier.issn	15723127	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/21486
dc.subject	Drop out	en
dc.subject	Poisson process	en
dc.subject	Randomization tests	en
dc.subject	Time to event	en
dc.subject	Trend tests	en
dc.title	Testing for undetected withdrawal in a follow-up study of times to events	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.stamet.2010.09.006	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.stamet.2010.09.006	en
heal.publicationDate	2011	en
heal.abstract	Undetected withdrawal of units from a study inflates the length of time remaining between the last recorded event and the end of the study. Treating these times as right-censored observations may give misleading results. A test is given for excessive remaining times assuming homogeneous Poisson processes, using approximations to the sum of Beta random variables. The distortion of trend tests by wrongly including these times in the analysis is examined and found to be substantial. On the other hand, the loss of power through unnecessarily dropping the time after the last event from the analysis is relatively insignificant, so the safest course is to discard these times. Tests for use when only one event per unit can be recorded are also considered. Simple randomization tests are shown to be effective in this case. © 2010 Elsevier B.V.	en
heal.journalName	Statistical Methodology	en
dc.identifier.doi	10.1016/j.stamet.2010.09.006	en
dc.identifier.volume	8	en
dc.identifier.issue	2	en
dc.identifier.spage	213	en
dc.identifier.epage	220	en