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Решение шага данных SAS может быть следующим:

/* set up data */
data have;
   infile datalines truncover;

   input activity_name      :         8.
         status_change_dttm : datetime20.
   ;

   format status_change_dttm datetime20.;

   datalines;
1 
1 
1 18FEB2019:19:16:13
2 
3 
3 
3 
4 
5 03FEB2019:14:38:52
5 04FEB2019:18:30:52
5 14FEB2019:12:00:12
15 
15 04FEB2019:18:30:52
15 14FEB2019:12:00:12
;


/* process and output */
data want;
   null_count  = 0;
   group_count = 0;

   /* count number of records and nulls for this activity_name group */
   do until(last.activity_name);
      set have;
      by activity_name;

      group_count + 1;

      if missing(status_change_dttm) then
         null_count + 1;
   end;

   /* output data for the same activity_name group */
   do until(last.activity_name);
      set have;
      by activity_name;

      if null_count = 0 then
         output;
      else
         if null_count eq group_count then
         do;
            output;
            /* prevent any more null records being output */
            null_count + 1;
         end;
         else
            if null_count lt group_count and not missing(status_change_dttm) then
               output;
   end;
run;