My data consists of measurements on patients with cancer and the variables are some indicators regarding the cancer as well as the stage and the grade of the cancer and some personal info about the patients. According to the doctors the missing values occured either because the part of the tissue they took from the patients was destroyed or because the doctor who did the biopsy didn't take a tissue sample big enough to estimate the stage of the cancer. Taking all these into account I have no reason to believe that the variables are MNAR and so two options remain, MAR or MCAR.
To my question now, let's say the MCAR is true (I read in another question that I can check this by doing a t-test, if someone knows another way please let me know) an easy way to deal with the missing values is to follow the complete-case method since the results will be unbiased, but my problem is that my data isn't big enough and if I delete cases I am afraid that the results probably won't be efficient. That's why I plan to do the MI but I'd like to know others opinion on that.