Once again, it could be caused by the air conditioner, could have been caused by the Petri dish, could have been caused by the lighting in the room. So no, because the study didn't have a treatment and a control group. Yeah, I would go with that one right over there. Yes, because she found the antibiotic kills more than 90% of the harmful bacteria. Once again, even if she knew for sure that more than 90% of the population had been killed, she doesn't know that it was caused by the antibiotic. It could have been caused by a whole bunch of things. If she had a control group that had the exact same conditions and the bacteria didn't die, then she could feel better that the bacteria death was due to the antibiotic.