19. Placebo group, because they’re testing it. Surgeries are known to work.
20. Surgery group, for the same reasons.
21. Knee functionality, because that (supposedly) DEPENDS on whether the patient gets a surgery or not.
22. Quantity and/or presence of tiger urine
23. Whether or not the deer are repelled, as that depends on the tiger urine.
24. Not sure for this one, sorry. It doesn’t look like there’s enough information present to identify a control group.
25. Sorry, but I’m not sure what this is. Hope the other answers help, though.