Calculation Using Case Data : All rows have 3 columns
    - Each row represents data from a case
    - Col 1 designates groups, 1,2,3, and so on
    - Col 2 is the number of intervals (seconds, hours, year, periods) the subject is in at the time of analysis
    - Col 3 is a single number. 0 represents that the subject had the index event (death, recurrence, discharge)
      during that interval, any other number represents that the subject has survived up to and
      including the interval

Calculation Using Event Table :
    - The rows are intervals (periods, days, years).
    - The columns designate events, each group has 2 columns, the first the number of subjects that
      experienced the index event during that interval (death, discharge, arrived),
      the second the number that survived that interval without the index event.