It's not a study, you can't have a control group in a retrospective review, you can only sort data from the data set. You can complain about the small N, though

It's not a study, you can't have a control group in a retrospective review, you can only sort data from the data set. You can complain about the small N, though. > Among ICU subjects, 11 (84.6%) had VDI, vs. 4 (57.1%) of floor subjects. Strikingly, 100% of ICU patients less than 75 years old had VDI (n=11; Table 2).