Note: Often, in smaller studies or studies that have multiple treatment groups with a small number of subjects per group, estimation of hazard ratios may not be possible or may lead to missing results. Hazard ratios are more reliable and useful when a study is appropriately sized for making such statistical comparisons.
Note: For
Mortality Time to Event, hazard ratios reflect comparisons between/among subjects that died only. Because of this, you can see hazard plots for gender or race or concomitant medications with missing plot points instead of having all possible values.