3 ms·

Perhaps I just don't know the correct terminology, though you can have multiple control groups, no? That is what I was meaning, I realize I wasn't very clear.

• saalweachter 13y ago
  Yeah, you can have multiple groups in the study, but you have to pick them somehow. Since most scientists aren't just sadistic mouse-torturers, you're picking groups that you think will tell you something. If you're testing a medicine, you might have one control (no-treatment) group, one group which receives whatever the current conventional/best drug is for the particular ailment, and one group which receives your new therapy. It's useful to see if your new therapy is any more effective than the old, in addition to seeing if it is effective at all. On the other hand, prior to this experiment, there was no reason to suspect that mice at 31C would be significantly different than mice at 25C. So why waste time, money, and mice by re-doing everything at 31C? Remember, things don't end well for the control group just because they're the no treatment group: they've got to be killed and autopsied at the same rate as the experimental group. When the study says "chemical X resulted in a 35% increase in tumors", they know that because they cut open both the experimental and control group, counted their tumors, weighed them, compared them, and came up with that number of 35%. Prior to this experiment, there was no reason to think that mice at 31C would be any different to mice at 25C, any more than you would expect mice wearing funny hats to be any different than mice without. Would you expect scientists to run a second control group of mice wearing funny hats, and slice them open and count their tumors, just in case it ended up being different?