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st: missing events in stset


From   Sara Mottram <s.mottram@cphc.keele.ac.uk>
To   statalist@hsphsun2.harvard.edu
Subject   st: missing events in stset
Date   Fri, 04 May 2007 09:08:07 +0100

Hi,

I am having some difficulty with -stset-. I'm almost certain that the fault lies with my data, as this same command has worked before in a similar dataset. However, I wonder if anyone could give me an idea as to where I might start looking to find the problem.

I have long data, identified by a variable surveyid. An event is a consultation with a doctor (kcons_post_3yr==1). Each person enters at their clinical assessment (edateass) and leaves at their censor time (censor_date). I know from a tabulation of the data that there are 734 consultations, but when I use -stset- it identifies 730 events. One person consults at time 0, so I think this person is being ignored - I understand this. However, this still leaves three events that are unidentified.

I have 742 people in the dataset so it is including everyone and I have checked that these consultations are not occurring after the censor date, so I don't think this is the problem. Also, I have checked that there are no missing values in any of the variables in the -stset- command.

Is there anything else that could obviously be causing this problem?

Best wishes
Sara


stset cons_dt, id(surveyid) fail(kcons_post_3yr==1) origin(time edateass) exit(time censor_date)

id: surveyid
failure event: kcons_post_3yr == 1
obs. time interval: (cons_dt[_n-1], cons_dt]
exit on or before: time censor_date
t for analysis: (time-origin)
origin: time edateass

------------------------------------------------------------------------------
16704 total obs.
28 obs. end on or before enter()
------------------------------------------------------------------------------
16676 obs. remaining, representing
742 subjects
730 failures in multiple failure-per-subject data
703420 total analysis time at risk, at risk from t = 0
earliest observed entry t = 0
last observed exit t = 1096

--
Sara Mottram
Research Assistant: Biostatistics
Primary Care Musculoskeletal Research Centre
Primary Care Sciences
Keele University
Staffordshire, ST5 5BG
Tel: +44 (0) 1782 584711
Fax: +44 (0) 1782 583911
Email: s.mottram@cphc.keele.ac.uk

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