Scientific experiments are a funny thing. When doing one, you need to have two groups — the control group and the experimental group. Heck, sometimes there can be multiple control groups (it's a common misconception that a control group has no intervention at all, or only a placebo—the control group may be getting a standard treatment, and more than one treatment may be approved). This is done to make sure that the results of the experiments actually come from the things the scientists are doing, and don't happen on their own due to the Placebo Effect or something in the test environment they weren't aware of.
Fictional scientists will never do this. If creating a race of monsters or trying to make a superhuman soldier, there will be no control group. All of the people will be turned into monsters or Super Soldiers, or die from the treatments.
Then again, most experiments in fiction are far-fetched enough that the purpose of a control group would be to make sure that people weren't just psychosomatically growing to 30 feet and shooting lasers out of their eyes. Of course, procedure is still procedure, and said experiments sometimes take place in worlds which do have people manifesting similar things quite spontaneously. In any case, the experimenters should be finding out how much of the treatment was necessary to display effects...
If time/funding/ego concerns whittle the testing down to just one person, then you get Professor Guinea Pig.
Sometimes this trope will be averted for Black Comedy or similarly humorous reason.
A real life application of this trope is experimental treatments conducted on terminally-ill patients: they know that they're dying, they've tried pretty much everything else, so they will willingly sign approval forms and let you start Playing with Syringes on the long shot that you might be able to save them. This is actually fairly rare, as even if the subject lives, the resultant information is of far less value without knowing exactly what you did that saved them... which is what you learn from the control group. (Well, that, and to make sure the 'treatment' didn't actually kill them faster.) The reason it's done at all is that it's considered unethical to deny possibly-lifesaving treatment from a terminally ill patient in order to use them as part of a control group.
- Averted in The Kids in the Hall movie Brain Candy, in a hilarious scene with Brendan Fraser as a guy with bad acne who knows he's in the placebo group.
- The film The Brain Machine, in which all four subjects are given the treatment.
- Night of the Lepus actually got that right. Now if only the annoying kid would not have swapped two rabbits, the film would never have happened.
- In Return of the Living Dead: Rave to the Grave, the female protagonist decides to experiment on a group of lab mice with a drug that turns people into zombies. She tells a fellow classmate that she'll set one mouse aside as a control group, and then in the next shot she goes back on her word and gives the drug to the control group. In a later scene, the classmate she lied to lets the mouse out because he thought it didn't have the drug, and ends up being bitten and turned into a zombie for his trouble while the mouse escapes to infect others. So not only did the protagonist violate scientific protocol that she was well aware of, but she lied about it and as a result endangered human lives and is directly responsible for at least part of the local Zombie Apocalypse.
- Averted in The Secret of NIMH, but only if you pay attention. During Nicodemus' flashback, the row below his is marked "CONTROL GROUP." It's difficult to see in the VHS version, however. It's more conspicuously averted in the original book.
- Averted in, of all things, the Z-Grade Minimum Opus UKM: The Ultimate Killing Machine, in which a group of 4-F "volunteers" are injected with a defective Super Soldier Serum without being informed just what it is they've "volunteered" for. The plot hinges on the fact that the four subjects were given varying doses of the Crazy Juice — and none of them know which one of them received just plain saline, as the control.
- V for Vendetta — The prisoners in the government facility were all exposed to experimental treatments. Not a single one of them seemed to be given placebo drugs. This is probably because, in the graphic novel, it was a parallel to Nazi Germany and the main object was to sadistically kill minorities using a face-saving rationale, not to do actual science. After all, for real science, half-starved and worked-nigh-to-death subjects are less than ideal.
- Averted in The Amazing Spider-Man: Dr. Connors administers his test serum to only one mouse and uses another as the control. The injected mouse mutates and eats the control mouse.
- Take to extremes in the zombie flick Devils Playground, in which not one of the thirty thousand volunteer test subjects is apparently given a placebo in lieu of the invigorating (and accidentally-zombifying) experimental drug.
- In the 2012 medical horror film The Facility, there are seven drug-test volunteers. Just one of them is a designated control subject, presumably because it aids the story if there's somebody audiences can be sure isn't going insane from the side effects. Another character is also spared the effects, as he chickened out and only pretended to take the drug.
- Averted in Larry Niven's Destiny's Road. Colonists on a new planet lack genetic diversity and a nutritious diet. They set aside one village to receive neither dietary supplements nor breeding opportunities, effectively turning the population into their control group.
- Max Barry's Machine Man has a laboratory's worth of scientists testing out an entire LINE of Better Parts on themselves. Better Spleens, Better Eyes, Better Muscles...
- In Stephen King's Firestarter Dr. Wanless tells the students that half of them will be receiving distilled water and the other half will be receiving a mildly hallucinogenic drug called "Lot 6", but it's made clear later on that all of the volunteers received "Lot 6". It is implied that he lied because he knew that there was a 50% mortality rate from the drug and he needed an excuse for why half of the participants in the study were gone the next morning.
- In Robert A. Heinlein's Beyond This Horizon (1942), most couples select the best sets of their genes for their children. But the government subsidizes a group designated as "Control Naturals" to create their children the old-fashioned way, in case current generations' definitions of "best" turn out to have unforeseen liabilities.
- Lack of control groups is at the center of the "miracle drug" in The King Of Torts. Doctors love the drug because it works very well and has no side effects. The drug company fears the drug because their lack of adequate testing failed to turn up the fact that the drug causes benign tumors in a user's bladder. Lawyers love the drug because they can use the drug company for damages and the treatment is very simple. Lawyers and users then hate the drug because the rushed treatments and settlements did not take the time to uncover the fact that the tumors are actually very malignant.
- Community episode "Social Psychology" has a test going on to observe the reaction of subjects to repeatedly being told to wait. The problem is the observation goes on in a group setting, when subjects should have been isolated from each other. Experiencing previous breakdowns may have influenced the breakdown of later subjects. Though given how the administrator reacts when one of them doesn't break down, and his amusement when others do, it's pretty clear this "experiment" was conducted for his own entertainment as much as anything.
- Speaking of having a control group yet still botching its implementation, in House, Thirteen is placed in the placebo group for a Huntington's Disease medication, which Foreman is able to find out by the nurse's small talk. Therefore, not only is the staff willing to spread this information around, said nurse even mentions that the real medication has a foul smell while the placebo doesn't, meaning they're trivially easy to tell apart which makes the whole exercise utterly pointless by countering the placebo effect.
- Also worth noting: in a proper double-blind medical study, no one knows which group is the placebo (or at least, not the people administering the medication) to prevent the researchers from accidentally giving the patients clues (for instance, through tone of voice or body language).
- Parodied in Sabrina the Teenage Witch: Sabrina's aunts have decided to live apart and Sabrina is seeing what would happen if she decided to stay with Zelda via magic crystal ball. She is shown becoming a scientist and giving anti-aging cream of her own design to a regular looking Libby (after she gives a speech insulting herself and praising Sabrina) and to a very old looking Mr. Kraft:
Mr. Kraft: Sabrina, you can be honest with me. I'm in the placebo group, aren't I?Sabrina: Maybe not. It's possible you were given aging cream. However, if you were you'd be suffering from hearing loss by now...Mr. Kraft: Oh, thank you. These are new shoes, actually.
- Subverted in The X-Files, the episode "Red Museum" gets this one right, a small town was being used to test one of the evil conspiracy's plans for turning people into half-alien monsters. The method being tested here was feeding them beef from cattle injected with alien growth hormones, which failed to turn them into aliens, but did turn several teenage boys into super-predatory rapists. The conspiracy guys also had one of their men establish a weird cult run out of a nearby farmhouse whose members were all vegetarians, in order to act as a control group. (We already know what happens if you feed people beef from cattle not injected with alien growth hormones.)
- Joked about by Dara O Briain on QI during a discussion of the mythical benefits of playing Mozart to children, where he points out the control group would be hard to find for that experiment.
Dara: So you're telling the parents 'we're going to deny your child intellectual stimulation in hopes that they turn out dumb.'
- A nice little aversion in Star Trek: Deep Space Nine where Sisko, Jake, Nog, and Quark are surveying a planet, Nog notes they are going to check other water sources to make sure the elements in the water they are reading isn't unique to the local area.
- Averted in Fallout: the Vault-Tec Vaults, despite their creators claiming they were for ensuring mankind's survival in the coming nuclear war, were secretly part of a grand social experiment by the government, each vault conducting a particular experiment (such as not letting the door close completely, overpopulating the vault, etc) with the purpose of the resulting data being used by said government in future space colonization. However, exactly 17 vaults (out of 122) worked exactly as advertised, said vaults being the control group.
- Portal 2 shows that Cave Johnson doesn't quite grasp how control groups are meant to work:
Cave Johnson: Alright, let's get started! This first test involves something the lab boys call "Repulsion Gel". You're not part of the control group, by the way. You get the gel. Last poor son of a gun got blue paint! Ha ha ha! ...all joking aside, that did happen. Broke every bone in his legs. Tragic, but informative! Or so I'm told. [A while later] The lab boys just informed me that I should NOT have mentioned the control group. They're telling me I ought to stop making these pre-recorded messages. That gave me an idea: Make more pre-recorded messages. I pay the bills here, I can talk about the control group all damn day!
- In the webcomic Inhuman, the Naitec scientists had no control group at first, but corrected this error a few years into their Tyke Bomb army project. Interestingly, they were exterminated not by their creatures, but by their theocratic clients.
- Humorously averted in this The Order of the Stick comic. A test group of captured peasants is to be pushed off a tower into a rift leading to the Sealed Evil in a Can; a control group is just going to be pushed off the other side of the tower.
- Averted in Girl Genius. Because being a mad scientist is not a good enough reason to tolerate lax procedures in your lab.
- Averted in this xkcd strip, with male sex partners serving as "control groups" for lesbian experimentation.
- El Goonish Shive: Averted. Tedd uses Sarah as a control test subject and is frustrated that he can't use Nanase as one since she's too Genre Savvy.
Tedd: Do you have any idea how statistically insignificant the amount of test data I have is?
- A Real Life example, attributed to Dr. E. E. Peacock, Jr.:
'One day when I was a junior medical student, a very important Boston surgeon visited the school and delivered a great treatise on a large number of patients who had undergone successful operations for vascular reconstruction.At the end of the lecture, a young student at the back of the room timidly asked, Do you have any controls? Well, the great surgeon drew himself up to his full height, hit the desk, and said, Do you mean did I not operate on half the patients? The hall grew very quiet then. The voice at the back of the room very hesitantly replied, Yes, thats what I had in mind. Then the visitors fist really came down as he thundered, Of course not. That would have doomed half of them to their death.God, it was quiet then, and one could scarcely hear the small voice ask, Which half?'
- Because of the ethical considerations of giving potentially dying people placebos and condemning them to death, many medical drug tests have a "control" group which receives the best known conventional treatment (the "gold-standard regimen") while the test group receives the new drug, and it's compared to the known rather than to completely untreated people.
- There have been more than a few cases of doctors deciding to forgo control groups in order to rush out a life-saving drug, only for it to be tragically realized later how ineffective and/or fatal it actually was.
- Centuries ago, an early doctor desperately tried to convince his contemporaries, who all had different treatments for the same disease, to start using control groups so they could work out, once and for all, which treatment was the best. Everyone refused, on the basis that their treatment was obviously the best, and they would not let their patients die. Well, just imagine how many lives could have been saved if scientists actually checked.
- This is believed to be the origin of the saying "stop it or you'll go blind". Because early sex researchers thought that "normal, respectable" people would be offended at the researchers questioning them about something as private as sex, the researchers decided to ask low-status people, most notably the blind housed in institutions. They found a high incidence of masturbation amongst the blind. Since there was no control group, people simply assumed that the high numbers were abnormal (they're not) and that the blindness was caused by masturbation. Or it may have just been a joke which some people took seriously. Nobody now knows for sure.
- As Victorian-era sexologists like Havelock Ellis and von Kraft-Ebbing were vocally frustrated with their society's squeamish refusal to acknowledge any form of human sexuality whatsoever for reasons of propriety, the (black) joke hypothesis could well have been the case. They were, after all, scientists who were trained in appropriate methodology note and who carefully trained others to treat the subject matter carefully and diligently.
- The dirty little secret about the Nazi death camps, one which all Western countries—and Russia—are unwilling to admit to, is that many of the experiments carried out on living people by the Nazis did indeed provide valid scientific knowledge of a sort which would have been impossible to recreate in any country with a normal regard for human rights. The Nazis systematically and ruthlessly tested concepts on living people, adhering rigidly to scientific protocols (including repeatability) and testing against "control groups". Much of their research on behalf of the Luftwaffe and Kreigsmarine involved replicating the effects of extreme temperature and pressure change on human bodies and human endurance. This involved pressure chambers in which the atmospheric effects of either extremely high flight or extremely low depths were tested on living people, with and without experimental flight-suits or diving/submarine apparatus. Nobody wants to admit how Nazi research still keeps our military pilots and submariners able to functionnote , but this, alas, is the truth.
- The Japanese "Unit 731" did more along these lines to advance the cause of science than the Nazis did, to the extent that they were essentially pardoned for war crimes in exchange for the data.
- In reality, not only do most scientific experiments not need control groups, in anything other than a biological setting the concept rarely makes sense at all. If you're testing whether a large or small cannonball will fall faster, for example, having a second pair of cannonballs that don't get dropped does not aid the experiment in any way.
- In addition, even in biological settings controls are not always necessary. If you are testing a serum to turn people into super-soldiers, there's no point in having a control group because we already know that people don't spontaneously turn into super-soldiers when given a placebo. Any such effect can only be the result of the serum, with no control group needed to know that. Control groups are only a necessity when looking for relatively small effects that can only be seen by statistically studying large groups. A serum to slightly increase sporting performance would need a control group to be sure any effect was not simply due to people unconsciously trying harder because they think they should be doing better after being injected with something. A serum that turns people into Captain America with an immediate large increase in muscle mass and the ability to run many times faster than any other human, not so much.
- As an example of why control groups are important, a study was done to test the effect of sport drinks (Gatorade and the like) on athletic ability. In the first test, the control group and the test subjects were given a drink: the control group got flavored water, and the test subjects the sport drink. Both ended up performing better, with no discernable difference in the increased ability. Scientists chalked it up to the placebo effect and were ready to call it a day. Then someone suggested having the groups "swig and spit", without actually drinking anything. The performance increase (and there was an increase) was exactly the same for both the test subjects and the control group, even though they weren't actually drinking anything. Result? Sports drinks don't actually help, but they can trick your body into thinking they're helping.