No Control Group

"[Caesars CEO Gary Loveman] likes to say there are three things that can get you fired from Caesars: Stealing, sexual harassment and running an experiment without a control group."

- NPR, 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. 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.

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 a Sight Gag 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.

Film

 * 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.
 * In Firestarter Dr. Wanless tells the students that half of them will be receiving distilled water (and the other half will be receiving a mildly hallucingenic 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).
 * 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.
 * Resident Evil.
 * In Return of the Living Dead 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 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.

Literature

 * 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...

Live Action TV
"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."
 * 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 themdoesn't break down and 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.
 * 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 accidentally (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 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:


 * Despite usually being the epitome of unscientific, The X-Files actually gets this one right. In the episode Red Museum, 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.
 * Except a proper control group in that case would consist of people being fed beef from cattle not injected with alien growth hormones.
 * We already know what happens if you feed people beef from cattle not injected with alien growth hormones. Vegetarians included.
 * But do we know what happens if you feed people in that area beef from cattle not injected with alien growth hormones, along with other food grown in that area? If you have a control group in all the same conditions, you get a more precise result.

Music Videos

 * Averted in the music video for Put It To The Test, by They Might Be Giants.

Real Life
"'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.
 * A Real Life example, attributed to Dr. E. E. Peacock, Jr.:

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. 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?”'"

Videogames
"Cave Johnson: Alright, let's get started! 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 said maybe I should stop making these prerecorded messages. That gave me an idea: Make more prerecorded messages. I pay the bills here, I can talk about the control group all damn day!"
 * Pretty much the main reason why Rapture became the way it did BioShock (series) when ADAM was found. The scientist that discovered it wanted to study it more for lasting effects. But Fontane pretty much pushed the product out the door to the masses. And well...you know the rest.
 * 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.
 * 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.
 * Portal 2 shows that Cave Johnson doesn't quite grasp how control groups are meant to work:

Web Comics

 * In the Web Comic 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 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.
 * Ironically, this may violate experimental procedure in a different way. A second variable introduced into the experiment is known as an procedural confound, and poses a danger to the validity of the experiment.
 * Of course, that particular variable would be a good test of Stockholm Syndrome.