st: On the interpretation of sts list and ltable in duration analysis

[Gijs Dekkers <gd@plan.be>]

Dear all,

I am applying the various lessons of the Essex summer school course on 
spell duration data (by Stephen Jenkins) to my own discrete paneldata set.
My problem is the following: Jenkins applies the commands 'sts list' and 
'ltable (noadjust)' in his lesson 4, and gets exactly the same output.

Unfortunately, in my case, this is not so. My question therefore is: how 
come that both commands give different results, where they do not in 
Jenkins' case? Am I doing something wrong? How should I interpret the 
results of both commands?

I have a simple discrete dataset of the following form:
id    year (called 'jaar2')     poor
1        1                            0
1        2                            0
1        3                            1
2        2                            0
2        3                            1
2        4                            1
and so forth.

Below follows the log file: I start with 'stset'-ting this data set, 
then I apply 'sts list', followed by 'ltable' including noadjust.

Here's what I have figured out so far: the number at risk (beg. total) 
is the number of individuals in 'sts list' whereas it is the number of 
observations in 'ltable' (in my case, that is, in Jenkins's course it is 
exactly the same thing). Moreover, those who fail (become poor) or net 
lost (censored) in 'sts list' add up to 'deaths' in 'ltable', which 
immediately raises the question on the meaning of 'lost' in ltable.

I would appreciate some help with this, as I am not an experienced user 
of stata.

Gijs

LOG-file:
------------------------------------------------------------------------------------------------
      log:  C:\usr\STATA\data\hazard.log
 log type:  text
opened on:  31 Mar 2005, 11:12:37

. use poverty.dta

. * bron: jenkins, lesson 3, page 6
. gen jaar2=jaar-1994 if (jaar<2003)

. stset jaar2, failure(poor) id(whhid)

               id:  whhid
    failure event:  poor != 0 & poor < .
obs. time interval:  (jaar2[_n-1], jaar2]
exit on or before:  failure

------------------------------------------------------------------------------
   17280  total obs.
    2182  obs. end on or before enter()
    2004  obs. begin on or after (first) failure
------------------------------------------------------------------------------
   13094  obs. remaining, representing
    3241  subjects
     454  failures in single failure-per-subject data
   17469  total analysis time at risk, at risk from t =         0
                            earliest observed entry t =         0
                                 last observed exit t =         8

. sts list

        failure _d:  poor
  analysis time _t:  jaar2
                id:  whhid

          Beg.          Net            Survivor      Std.
 Time    Total   Fail   Lost           Function     Error     [95% 
Conf. Int.]
-------------------------------------------------------------------------------
    1     3241    109    162             0.9664    0.0032     0.9596    
0.9720
    2     2970     87    226             0.9381    0.0043     0.9291    
0.9459
    3     2657     72    214             0.9126    0.0051     0.9021    
0.9221
    4     2371     59    404             0.8899    0.0058     0.8780    
0.9007
    5     1908     26    177             0.8778    0.0062     0.8651    
0.8894
    6     1705     27    212             0.8639    0.0066     0.8503    
0.8763
    7     1466     42    273             0.8392    0.0075     0.8239    
0.8532
    8     1151     32   1119             0.8158    0.0083     0.7989    
0.8315
-------------------------------------------------------------------------------

.
end of do-file

. do "C:\windows\TEMP\STD040000.tmp"

. ltable jaar2 poor, noadjust

                Beg.                                 Std.
  Interval     Total   Deaths   Lost    Survival    Error     [95% 
Conf. Int.]
-------------------------------------------------------------------------------
   0     1     17280      217   1965     0.9874    0.0008     0.9857    
0.9890
   1     2     15098      231   1934     0.9723    0.0013     0.9697    
0.9748
   2     3     12933      240   2072     0.9543    0.0017     0.9508    
0.9575
   3     4     10621      225   1927     0.9341    0.0021     0.9297    
0.9381
   4     5      8469      208   1979     0.9111    0.0026     0.9059    
0.9161
   5     6      6282      145   1587     0.8901    0.0031     0.8839    
0.8960
   6     7      4550      144   1485     0.8619    0.0038     0.8543    
0.8692
   7     8      2921      155   1372     0.8162    0.0051     0.8060    
0.8259
   8     9      1394      141   1253     0.7336    0.0080     0.7176    
0.7490
-------------------------------------------------------------------------------

.
end of do-file


--
Dr. Gijs Dekkers
Federaal Planbureau
Algemene Directie
Kunstlaan 47-49
B 1000 Brussel
++32/(0)2/5077413
fax  7373
	





**********************************************************************
Disclaimer: This e-mail may contain confidential information
which is intended only for the use of the recipient(s) named above.
If you have received this communication in error, please
notify the sender immediately and delete this e-mail from
your system.
Please note that e-mail messages cannot be considered as official
information from the Federal Planning Bureau.
**********************************************************************
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/