EffDesign               HCT design with interim monitoring for efficacy
                        only
EffIM                   Monitoring the trial at interim looks for a
                        trial with efficacy monitoring only
FutDesign               HCT design with interim monitoring for futiity
                        only
FutIM                   Monitoring the trial at interim looks for a
                        trial with futility monitoring only
HCTSurvDesign           HCT design with interim monitoring for both
                        efficacy and futility
IM                      Monitoring the trial at interim looks for a
                        trial with efficacy and futility boundaries
SM                      Sample size in terms of number of subjects in
                        the experimental group
calendar_time           Calculate Calendar Times for Interim Analysis
                        Looks
sf                      Log rank test for non-inferiority trial
