A study was conducted to compare the effectiveness and safety of two different treatments in patients with chronic kidney disease. To validate the hypothesis that the 2 treatments were equivalent, 32 patients with kidney disease were equally divided into two groups (group A and Group B), and they were randomly assigned to methylprednisolone alternated with a cytotoxic drug every other month for 6 months (group A) or to intramuscular synthetic adrenocorticotropic hormone administered twice a week for 1 year (group B). The primary outcome measure is cumulative number of remissions. After a median follow-up of 24 months (interquartile range, 15 to 25 months), there were 4 complete in group A versus 8 complete remissions in group B. Some of the demographic and histological characteristics of patients from Group A are given below: image.png Is this an observational or experimental study? According to the study in Question #2, write down the population and the sample