The PRED_MRG output group in SURVIVAL consists of the estimate
of the predicted marginals, standard error of PREDMRG estimates, T-statistic
(PREDMRG /SE(PREDMRG)) and P-value for the test of hypothesis H0:PREDMRG=0.
This group is not printed by default, though the statistics are available
for individual printing, either by explicit use of appropriate keyword(s)
on the PRINT statement or by
PRED_MRG=DEFAULT or PRED_MRG=ALL on the PRINT statement. The keywords
in the PRED_MRG group are listed below in default order.