What I would like to know is if the total time in the incidence rate denominator is the sum of all times or the longest follow up time. just need to know how to calculate the denominator for incidence rate.   I did this:   proc sort; by sex; proc print; var time; sum time; by sex; run;   and it added up time ind ays for all females and males separately. is this correct?     thanks   ... View more

thanks!   data b; set a; input sex $ eventtype time; datalines; m  1       3000 f    1       3996 f    1       285  m   2      4000 m   3      893 m   2      1000 m   2      3952 f     1      123  f     1      964 m   1      478 m   2      2789 ; run;   note: eventtype: 1=contralateral major amputation (MAIN outcome of interest); 2=death; 3=migration from country time is time to event (contralaterl major amputation/death/migration) from T0 (30 days after surviving a unilateral major amputation) in days   I want to calculate incidence of contralateral major amputation per 100 person years among males and females separately.   thank you K    ... View more