[[quoteright:347: http://static.tvtropes.org/pmwiki/pub/images/dentists_1674.jpg]][[caption-width-right:347:Image by [[http://www.grimm.ca/ Ileana Grimm]].]]

->''"Four out of five doctors [[TheSmokingSection prefer Camels]]. The fifth prefers women."''

Stock phrase in commercials for non-prescription products with some purported health benefit -- especially items which are not actually health care items, such as sugar-free gum.

Sometimes phrased as "Nine out of ''these'' ten doctors agree," showing you a group of men in white coats with stethoscopes. This is a clue to what's really going on.

Your brain hears "Nine out of Ten Doctors Agree", and reads it as "90% of doctors agree." But that's not necessarily what happened -- the sample size and population can be anything the advertiser wants it to be, including literally having a panel of only ten doctors asked (and cherrypicking doctors until they get the result they want).

Alternatively, the claim may reflect reality, but what is being claimed isn't the same as what is being sold: listen carefully. Did nine out of ten dentists really say that their brand of toothpaste was best, or did nine out of ten dentists just agree that ''toothpaste in general'' is a good idea? Did they say they would recommend ''this'' brand over all other brands, or did they just say they would recommend it?

In fact, if you catch wise to the fact that what the nine of ten doctors are agreeing to is something much more generic than what is being sold, you might start to wonder: What's up with the ''one'' out of ten doctors who thinks smoking is cool?

As a result, it has in recent years become fashionable for some commercials to poke fun at the trope, implying that the tenth doctor ''would'' have endorsed their product, were it not for some external force (he was reaching for the "agree" button when a poisonous snake bit him, sending him into a convulsion before he could agree).

For the classic disassembly of these sort of statistics, may we recommend Darrell Huff's ''How to Lie with Statistics''? The 1950s were a lot less naive than you might assume. And indeed, this is a subtrope of LiesDamnedLiesAndStatistics.

This trope has nothing to do with Literature/DoctorDolittle, SelfDemonstrating/DoctorDoom, [[ComicBook/SpiderMan Doctor Octopus]], Theatre/DoctorFaustus, [[WebVideo/DoctorHorriblesSingAlongBlog Doctor Horrible]], DoctorPhil, Manga/DoctorSlump, Comicbook/DoctorStrange, Film/DrStrangelove, ComicBook/DoctorFate, Literature/DoctorZhivago, [[Literature/TheStrangeCaseOfDrJekyllAndMrHyde Doctor Jekyll]], [[VideoGame/MegaMan Doctor Wily]], [[ComicBook/{{Watchmen}} Doctor Manhattan]], [[VideoGame/SonicTheHedgehog Dr. Eggman]], Music/DoctorSteel, [[WitchDoctor witch doctors of any denomination]], or any of the Doctors from Series/DoctorWho because it's NotThatKindOfDoctor, though you probably could find something at least nine of them agreed on.
* The original instance of this phrase comes from Trident gum, where "four out of five dentists recommended sugarless gum for their patients who chew gum". They didn't add the qualifier "if their patients ''insisted'' on chewing gum", nor did they tell you that [[http://www.straightdope.com/classics/a1_174a.html the fifth dentist recommended that his patients not chew gum at all]].
** Years later, Trident would parody this device by having four out of five dentists endorse the gum, with the fifth accidentally denouncing it (being knocked unconscious and landing his face on the "NO" button, [[SquirrelsInMyPants having a squirrel crawl up his leg]] and [[GroinAttack bite him in the groin]], causing him to yell [[BigNo "Nooooooo!"]] etc.).
** This was parodied on an early episode of ''{{Friends}}'' - someone enters and says "Guess what!" and Chandler immediately quips, "The fifth dentist caved, and now they're all recommending Trident?"
** It was also parodied in a 2004 ''Series/CornerGas'' episode when Wanda admitted that she hadn't seen a dentist since 1992. Brent said, "Well, you should really try to squeeze in a visit every decade or so. Four out of five dentists recommend seeing a dentist. I don't know what the fifth guy's thinking."
** Comedians like to point out that "Trident" means "three teeth".
* The legendary StanFreberg parodied this as far back as the early 1960s with a commercial he made for Chun King Chinese food which proudly proclaimed that nine out of ten doctors recommended the product. The camera then revealed nine smiling Chinese doctors and one scowling Anglo one.
* An extreme example: an ad for Whiskas claimed that "8 out of 10 Cats prefer Whiskas." This was later changed to "8 out of 10 owners who expressed a preference said that their cats preferred Whiskas." "who expressed a preference" means there could be twenty thousand cats who'll eat anything for every eight Whiskas lovers, but they don't count. Another way to look at it is that it's entirely plausible 8 out of 10 cats would prefer Whiskas to, let's just say: starvation, being hit with a brick, being burned alive, [[ArsonMurderAndJaywalking or a bath]].
** This is actually gave the name to the Channel4 PanelShow ''Series/EightOutOfTenCats'', which is all about statistics and opinion polls.
* The Swedish humorist site [[http://www.skrattnet.se/ Skrattnet]] used to have a tagline that translates into "Skrattnet, because 20 out of 10 schizophrenics recommend us.".
* Parodied by DavidLetterman on his talk show, when he claimed that "3 out of 4 Americans make up 75% of the population."
** Similarly, ''Music/LesLuthiers'' give us this: "Out of every ten television viewer, five... are half of them".
* [[http://uncyclopedia.org/wiki/One_Out_of_Ten_Doctors This]] uncyclopedia article, supposing on the answer to what the one out of ten doctors do recommend (leeching and eye of newt for allergy medication and the like..)
* Parodied when ''Series/TheGoodies'' go into the advertising business in "It Might As Well Be String".
-->'''Tim:''' Look at this! Nine out of every ten doctors agree that people who don't eat Sunbeam sliced bread will get squashed by elephants!
-->'''Graeme:''' That's right. Mind you, it did take us a long time to find the right nine doctors, woo hoo hoo (makes loony signal) ... and the elephants!
* ''PearlsBeforeSwine'' had a few comics where Pig introduced his friends, five doctors, four of which agreed on everything, the fifth of which always disagreed. This was for more than just chewing gum -- they went to a funeral, and while the first four were offering their condolences, the fifth one just said, "She's dead all right."
* A strip in ''Webcomic/LegostarGalactica'' has this. It turns out that the doctor being talked to is the tenth.
* Humorous advertising-deconstruction program ''{{The Gruen Transfer}}'' has actually registered the company "Nine Out Of Ten Experts", and are offering the company's endorsement to products for a "small fee". Nine Out Of Ten Experts recommend The Gruen Transfer.
* A commercial for Tylenol stated that "9 out of 10 doctors recommend Tylenol!" The ''very next'' commercial was for Advil, stating "4 out of 5 doctors prefer Advil!" For all we know, the 10th/5th doctor just goes "What d'ya got?" After all, it's reasonable to expect you to keep on hand the one that ''works'' for you.
** These claims aren't necessarily mutually incompatible ... it's what goes unsaid ("in a hospital setting where we can monitor you to make sure it's not killing your liver," for example) that makes the difference.
* From Music/LemonDemon's "Hyakugojyuuichi 2003": "Nine out of ten sociopaths agree / You gotta see [[WebAnimation/{{Animutation}} Hyakugojyuuichi]]." How's that for meter?
* Yet another parody, in ''SamAndMax: Reality 2.0'':
-->'''Max''': ''(describing what happened to a beat-up gumball machine)'' A gang of five dentists came through the other night, and four of them just started beating the hell out of it!\\
'''Sam''': What did the fifth one do?\\
'''Max''': He kept sobbing, and saying, "Why can't we all just get along?"
* ''Series/RobocopTheSeries'' has an interesting example, nine out of ten doctors ''employed by a MegaCorp'' recommend a drug, clearly in an attempt to invoke the trope.
* Dying after beaming into a toxic atmosphere in ''SpaceQuest V'' results this quote, "4 out of 5 doctors agree that beaming into a toxic atmosphere without the proper equipment can be hazardous to your health."
* A variation: speaking of ''Series/DoctorWho'', a wonderful FunTShirt found online has "9 out of 10 Doctors agree, [[LargeHam the 10th Doctor]] [[HotBlooded should mellow out.]]"
** Another version: "9 out of 10 doctors agree: [[Creator/TomBaker Four]]'s scarf is too long."
* Colin Mochrie on ''Series/WhoseLineIsItAnyway'':
--> "[[http://www.youtube.com/watch?v=oCdkV8MOcDQ Nine out of ten Americans agree that out of ten Americans, one will disagree with the other nine!]]"
** Or how about: "Nine out of 10 doctors agree the tenth one should really chill out"
** And also: "Nine out of ten dentists leaves one dentist."
* On February 15 2008, a news anchor on ''Radio/RoyalCanadianAirFarce'' said, "A survey shows 51% of Canadians believe there is such a thing as {{love at first sight}}. The other 49% are men."
* A strip of ''ComicStrip/NineChickweedLane'' showed a group of white-coated figures walking away from another whom they'd apparently just hanged (only his legs are shown, dangling from the top of the panel), and an onlooker remarking, "Nine out of ten doctors agreed."
* A humorous variant in ''VideoGame/MassEffect2'':
--> '''Tupari Drinks Machine:''' "Nine out of ten Tupari drinkers recommend Tupari to their friends. '''THE LAST ONE IS''' '''''ON MY LIST.'''''"
* Played for laughs in ''VideoGame/AssassinsCreedBrotherhood'': a doctor who's treating your bullet wounds will mention that four out of five doctors would use leeches, lucky for you he's the fifth.
* That's what happens to the 10th doctor [[http://1.bp.blogspot.com/-fhetbwvmhJw/TfrLZSSj8mI/AAAAAAAAD3k/h4fAN-z5Lt8/s1600/Dentista-2.jpg]]
* [[http://www.youtube.com/watch?v=2ArIj236UHs Did you know]] that eight out of five dentists say that studying in the library is 6 bajillion times more effective than studying in your shower?
* One ''Magazine/{{Mad}}'' cartoon had a group of dentists cheerfully saying "Brush after every meal!" with one surly-looking holdout muttering "I'm sure you have better things to do with your time."
* Another FunTShirt. "Six out of seven dwarfs aren't [[Disney/SnowWhiteAndTheSevenDwarfs Happy]]."
* ''Literature/HitherbyDragons'': in the short story [[http://imago.hitherby.com/2006/02/no-actual-bears-were-harmed/ "No Actual Bears Were Harmed"]], Jane goes on a quest to confront the tenth dentist, because his approval is needed to bring Baldur back to life. However, Dentist 10 has a (tragic) reason not to approve of ''anything''...
* ''WesternAnimation/SpongebobSquarepants'' has the 50s Krusty Krab ad with this line:
--> Yes folks, nine out of ten doctors recommend eating at least one Krabby Patty a day to maintain a healthy lifestyle and a youthful positive attitude.
* ''Anime/PokemonMewtwoReturns'': Misty and Brock drink some water from the Purity River and love the taste. Ash drinks it and says it tastes "like something's been swimming in it." Pikachu and Togepi try it and love it.
--> '''Misty:''' Looks like four out of five water drinkers prefer Purity River water.
* Parodied by ''WebVideo/FiveSecondFilms''. "[[http://www.youtube.com/watch?v=bEJsDSElKD4 Nine out of ten scientists agree...]] guns are dangerous." The nine scientists then use their guns to hunt down and kill the tenth one who disagreed.
* An odd/extremely fraudulent add from Website/{{Quackwatch}}: [[http://www.quackwatch.org/01QuackeryRelatedTopics/PhonyAds/antioxad.html this 1994 ad]] purports to be based on a poll where 8 out of 10 doctors questioned use antioxidants for their health; the "poll" was actually a study on the letters sent to a trade magazine for doctors, with 8 of 10 letters talking positively of antioxidants.