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help for ^sttocc^                                       (STB-40.1: ssa10.1)
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Generating a case-control study from a cohort study by sampling the risk sets
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^sttocc^ varlist, [^fc^odes^(^codes^)^ ^or^igin^(^varname | number^)^
        ^sc^ale^(^varname | number^)^ ^by(^varlist^)^ ^m^atch^(^varlist^)^
        ^n^umber^(^#^)^ ^gen^erate^(^varlist^)^


Description
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A cohort study can be used to generate a case-control study, nested
in the cohort study, by sampling the cohort for controls.
For each case the controls are chosen from those members
of the cohort who are at risk at the failure time of the case, that is
from the risk set corresponding to the case. The case-control
study so formed is matched with respect to the time scale used to
compute risk sets.


Options
-------

^fcodes( )^ specifies the codes to be treated as failures,
all others to be treated as censoring. 

^scale( )^specifies the units for the analysis time scale - that is, 
units for y, the rate denominator. 

^match( )^ specifies additional categorical variables for matching 
controls to cases.

^n( )^ specifies the number of controls to draw for each case. The default
is 1, even though this is not a very sensible choice!

^generate( )^ specifies variable names for three generated variables.
These are (with their default names) (i) a case-control indicator
coded 0 for controls and 1 for cases (^_case^), (ii) a case-control
set identifier (^_set^), and (iii) the time, on the analysis scale at
which the set was constructed, that is the failure time of the case (^_time^). 


Examples
--------

^sttocc, origin(dob) scale(365.25) match(job) n(5)^


Authors
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      David Clayton
      MRC Biostatistical Research Unit
      Cambridge
      email: david.clayton@@mrc-bsu.cam.ac.uk

      Michael Hills
      London School of Hygiene and Tropical Medicine (retired)
      email: mhills@@regress.demon.co.uk


Also see
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    STB:  STB-41 ssa10.1, STB-40 ssa10
On-line:  help for @mhodds@, @logistic@, @clogit@