->''[Caesars CEO Gary Loveman] likes to say there are three things that can get you fired from Caesars: [[ArsonMurderAndJaywalking Stealing, sexual harassment and running an experiment without a control group.]]''
-->NPR, [[http://www.npr.org/blogs/money/2011/11/15/142366953/the-tuesday-podcast-from-harvard-economist-to-casino-ceo From Harvard Economist To Casino CEO]]

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. 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 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 [[SuperSoldier superhuman soldier]], there will be no control group. All of the people will be [[WasOnceAMan 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 ''[[MagicFeather psychosomatically]]'' [[AttackOfTheFiftyFootWhatever growing to 30 feet]] and [[EyeBeams 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 ProfessorGuineaPig.

Sometimes this trope will be averted for a SightGag or similarly humorous reason.

A real life application of this trope is [[EmergencyTransformation 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 PlayingWithSyringes 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 [[CaptainObvious 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.
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!!Examples:

[[foldercontrol]]

[[folder:Film]]
* Averted in TheKidsInTheHall movie ''Film/BrainCandy'', in a hilarious scene with Creator/BrendanFraser 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.
* ''Film/NightOfTheLepus'' actually got that right. Now if only the annoying kid would not have swapped two rabbits, the film would never have happened.
* In ''ReturnOfTheLivingDead 5: Rave From 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 ZombieApocalypse.
* Averted in ''TheSecretOfNIMH'', [[FreezeFrameBonus 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 [[SuperSerum 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.
* ''Film/VForVendetta'' -- 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 NaziGermany 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 ''Film/TheAmazingSpiderMan'': Dr. Connors administers his test serum to only one mouse and uses another as the control. [[spoiler:The injected mouse mutates and eats the control mouse.]]
* Take to extremes in the zombie flick ''Devil's 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.
[[/folder]]

[[folder:Literature]]
* Averted in Creator/LarryNiven'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 ''MachineMan'' has a laboratory's worth of scientists testing out an entire LINE of Better Parts on themselves. Better Spleens, Better Eyes, Better Muscles...
* In Creator/StephenKing's ''Literature/{{Firestarter}}'' [[MadScientist 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" (which induces a wide variety of psychic powers in the subjects, some of which are permanent -- not to mention acting as a mutagen which produces even stronger results in the children of those who receive it). Although there isn't much need to cancel the placebo effect if you don't tell the subjects what are they actually getting...
* In Creator/RobertAHeinlein's ''Literature/BeyondThisHorizon'' (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.
[[/folder]]

[[folder:Live Action TV]]
* ''Series/{{Community}}'' episode "[[Recap/CommunityS1E04SocialPsychology 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 ''Series/{{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 ''Series/SabrinaTheTeenageWitch'': 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 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 ''Series/TheXFiles'', 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.)
* A nice little aversion in ''StarTrekDeepSpaceNine'' where Sisko, Jake, Nog, and [[ItMakesSenseInContext 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.
[[/folder]]

[[folder:Music Videos]]
* Averted in the [[http://www.youtube.com/watch?v=_cCC8a6HMz4 music video]] for Put It To The Test, by TheyMightBeGiants.
[[/folder]]

[[folder:Video Games]]
* Averted in ''VideoGame/{{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.
** Further, when nuclear war did happen, these experiments were all that were available to commoners, but there were two other vaults (one for Vault-Tec employees and one for the U.S. Government) that high level personnel got access to; they had different layouts and much more stable construction.
* ''VideoGame/{{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 [[CaptainObvious 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. [[ScrewTheRulesIHaveMoney I pay the bills here, I can talk about the control group all damn day]]!
[[/folder]]

[[folder:Web Comics]]
* In the {{webcomic}} ''Inhuman'', the Naitec scientists had no control group at first, but corrected this error a few years into their TykeBomb army project. Interestingly, they were exterminated not [[HoistByHisOwnPetard by their creatures]], but by their theocratic clients.
* Humorously averted in [[http://www.giantitp.com/comics/oots0545.html this]] ''WebComic/TheOrderOfTheStick'' comic. A test group of captured peasants is to be pushed off a tower into a rift leading to the SealedEvilInACan; a control group is just going to be pushed off the other side of the tower.
* [[http://www.girlgeniusonline.com/comic.php?date=20090706 Averted]] in ''Webcomic/GirlGenius''. Because being a ''[[MadScientist mad]]'' scientist is not a good enough reason [[http://www.girlgeniusonline.com/comic.php?date=20040223 to tolerate lax procedures in your lab]].
** Ironically, this may violate experimental procedure in a different way. A second variable introduced into the experiment is known as a [[http://en.wikipedia.org/wiki/Confounding procedural confound]], and poses a danger to the validity of the experiment.
*** Of course, ''that'' particular variable would be a good test of StockholmSyndrome.
* Averted in [[http://xkcd.com/507/ this]] Webcomic/{{xkcd}} strip, with male sex partners serving as "control groups" for [[ExperimentedInCollege lesbian experimentation]].
[[/folder]]

[[folder:Real Life]]
* A RealLife example, [[http://lesswrong.com/lw/37k/rationality_quotes_december_2010/35rk 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, that’s what I had in mind.” Then the visitor’s fist really came down as he thundered, “Of course not. [[EmergencyTransformation 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 ([[ScienceMarchesOn they're not]]) and that [[FalseCause the blindness was caused by masturbation.]] Or it may have just been a joke which some people took seriously. Nobody now knows for sure.
[[/folder]]

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