Toilet paper orientation

Toilet paper orientation
The over orientation
The under orientation

Toilet paper when used with a toilet roll holder with a horizontal axle parallel to the floor and also parallel to the wall has two possible orientations: the toilet paper may hang over (in front of) or under (behind) the roll; if perpendicular to the wall, the two orientations are right-left or near-away. The choice is largely a matter of personal preference, dictated by habit. In surveys of US consumers and of bath and kitchen specialists, 60–70 percent of respondents prefer over.[1]

While many people consider this topic unimportant, some hold strong opinions on the matter. Advice columnist Ann Landers said that the subject was the most responded to (15,000 letters in 1986) and controversial issue in her column's history. Defenders of either position cite advantages ranging from aesthetics, hospitality, and cleanliness to paper conservation, the ease of detaching individual squares, and compatibility with a recreational vehicle or a cat. Some writers have proposed connections to age, sex, or political philosophy, and survey evidence has shown a correlation with socioeconomic status.[2] A generic answer is that it should hang the way the person doing the roll changing prefers.

Solutions range from compromise, to using separate dispensers or separate bathrooms entirely, or simply ignoring the issue altogether. One man advocates a plan under which his country will standardize on a single forced orientation, and at least one inventor hopes to popularize a new kind of toilet roll holder which swivels from one orientation to the other.[3]

Context and relevance

In the article "Bathroom Politics: Introducing Students to Sociological Thinking from the Bottom Up",[4] Eastern Institute of Technology sociology professor Edgar Alan Burns describes some reasons toilet paper politics is worthy of examination. On the first day of Burns' introductory course in sociology, he asks his students, "Which way do you think a roll of toilet paper should hang?"[5] In the following fifty minutes, the students examine why they picked their answers, exploring the social construction of "rules and practices which they have never consciously thought about before".[6]

Burns' activity has been adopted by a social psychology course at the University of Notre Dame, where it is used to illustrate the principles of Berger and Luckmann's 1966 classic The Social Construction of Reality.[7] Similar everyday topics that have been used to awaken the sociological imagination include games of tic-tac-toe, violations of personal space, the rules of walking, and the etiquette of which urinals men choose in public restrooms.[8]

Christopher Peterson, a professor of psychology at the University of Michigan, classifies the choice of toilet paper orientation under "tastes, preferences, and interests" as opposed to either values or "attitudes, traits, norms, and needs". Other personal interests include one's favorite cola or baseball team. Interests are an important part of identity; one expects and prefers that different people have different interests, which serves one's "sense of uniqueness". Differences in interests usually lead at most to teasing and gentle chiding. For most people, interests don't cause the serious divisions caused by conflicts of values; a possible exception is what Peterson calls "the 'get a life' folks among us" who elevate interests into moral issues.[9]

Morton Ann Gernsbacher, a professor of psychology at the University of Wisconsin–Madison, compares the orientation of toilet paper to the orientation of cutlery in a dishwasher, the choice of which drawer in a chest of drawers to place one's socks, and the order of shampooing one's hair and lathering one's body in the shower. In each choice, there is a prototypical solution chosen by the majority, and it is tempting to offer simplistic explanations of how the minority must be different. She warns that neuroimaging experiments—which as of 2007 were beginning to probe behaviors from mental rotation and facial expressions to grocery shopping and tickling—must strive to avoid such cultural bias and stereotypes.[10]

In his book Conversational Capital, Bertrand Cesvet gives toilet paper placement as an example of ritualized behavior—one of the ways designers and marketers can create a memorable experience around a product that leads to word-of-mouth momentum. Cesvet's other examples include shaking a box of Tic Tacs and dissecting Oreo cookies.[11]

Broadcaster Jim Bohannon, who once spent an hour on toilet paper orientation, explains that such issues are good for talk radio: "It is an interactive medium, a certain kind of clash, it doesn't have to be a violent clash, but at least a disagreement would certainly be at the top of the list. It has to be something that's of general interest."[12]

Arguments for over or under

Folded and sealed toilet paper with cover, Hotel Monasterio 2009
Paper mounted under with upside-down images and text

The main reasons given by people to explain why they hang their toilet paper a given way are ease of grabbing and habit.[13] Some particular advantages cited for each orientation include:

Partisans have claimed that each method makes it easier to tear the toilet paper on a perforated sheet boundary, depending on the direction of pulling and the use of a second hand to stabilize the roll.[22] (A traveller from the U.S. to China in 1991 noted a different setup: non-perforated paper with a metal cutter above the roll, which obliges the over direction.)[23]

It is unclear if one orientation is more economical than the other. The Centralian Advocate attributes a claim that over saves on paper usage to Planet Green.[24] A reader of The Orange County Register found a "six-month study" by a "university in the U.S." that came to the same conclusion.[25] But a reader of the Cape Argus wrote that a "British loo paper manufacturer" came to the opposite conclusion.[26] In his humor compilation How Hemlines Predict the Economy, Peter FitzSimons writes that placing the hanging flap against the wall "is generally twice as economical".[27]

In the academic field of evaluation, Michael Scriven writes that the question of the correct way to insert toilet paper is a "one-item aptitude test" for measuring one's evaluation skills. These skills include the evaluative attitude, practical logical analysis, empathy, teaching, and being a quick study. To prove one's competence, one may either derive the "one right answer" or prove that the test is or is not culturally biased.[28]

Preliminaries

In their 2006 book Why Not?, Barry Nalebuff and Ian Ayres write that the debate over toilet paper is a debate about symmetry (they also write that too much paper has been wasted on the issue, and that they prefer over). By taking an approximately symmetric situation and flipping it around, one can sometimes arrive at a new solution to a problem with its own surprising advantages. Other physical examples include peeling a banana from the apex rather than the pedicel, or steering a car from the rear rather than the front.[29]

There is a reflection symmetry between the left and right sides of the roll, so whether it rotates clockwise or counterclockwise is ambiguous; it depends on one's point of view.[30] The up/down and front/back symmetries are broken by the force of gravity and the locations of the wall and the user, so one can distinguish between two orientations:

There are other everyday objects that dispense a sheet of material from a roll: fax machines, cash registers, plastic wrap, aluminum foil, and parchment paper. One columnist who believes in the importance of toilet paper orientation writes, "all have to exit in the correct direction or it doesn't work, or you cut yourself, or both."[31]

Preferences

Multi-orientable toilet paper holder
Another solution: two paper holders, even with different toilet paper.

Survey results

The question "Do you prefer that your toilet tissue unwinds over or under the spool?" is featured on the cover of Barry Sinrod and Mel Poretz's 1989 book The First Really Important Survey of American Habits. The overall result: 68 percent chose over.[32] Sinrod explained, "To me, the essence of the book is the toilet paper question ... Either people don't care, or they care so much that they practically cause bodily injury to one another."[33] Poretz observed, "The toilet-paper question galvanizes people almost like the Miller Lite tastes-great/less-filling commercial."[34]

In Bernice Kanner's 1995 book Are You Normal?, 53 percent of survey respondents prefer over, while "a fourth" prefer under and 8 percent do not know or care.[35]

Sitting Pretty: The History of the Toilet, a travelling exhibition that tours Canadian museums, asks visitors to register their preferred roll direction. When the exhibition reached Huntsville, Ontario, in June 2001, 13,000 visitors had taken the survey, with 67 percent preferring over.[36] At the Saint Boniface Museum in Winnipeg in February 2005, a voting machine registered 5,831 over versus 5,679 under, or 51 percent over. Saint Boniface's director noted, "I think there's been some cheating, though."[37]

Georgia-Pacific commissioned a survey of Americans' bathroom habits in 1993 to launch its new Quilted Northern brand, and more surveys followed:[38]

In 1993, American Standard Brands conducted a poll of "designers, contractors, dealers, distributors and other bath and kitchen reps"[45] at the Kitchen/Bath Industry Show & Conference in Atlanta. The question: "What is the correct and only way to hang the toilet paper – under or over?"[46] Over won 59 percent of the vote, 1,826 to 1,256.[45] American Standard spokeswoman Nora Monroe observed, "The bathroom is a territorial place. You'd be surprised how many people have definite opinions on this issue."[47] In 2008, American Standard commissioned the 2008 Bathroom Habits Survey, a more traditional format conducted by Opinion Research Corporation with 1,001 respondents. This time, "three-quarters" answered over.[48]

In 1995, a survey by Scott Paper Company's "Cottonelle College of Freshness Knowledge" had "most Americans over 50" preferring over.[49] In another Cottonelle survey in 1999, 68 percent of respondents preferred over to 25 percent under. Columnist Bonnie Henry hypothesizes of the others: "Meanwhile, 7 percent – no doubt bored beyond belief at this point by the inane questioning – had slipped into a deep, irreversible coma."[50]

On January 27, 2010, the 100th anniversary of Thomas Crapper's death,[13] Cottonelle launched a "Great Debate" advertising campaign, inviting American consumers to vote their preference at a Kimberly-Clark website.[51] The result was announced during the 82nd Academy Awards: 72 percent had voted over.[52] In a more traditional preliminary survey of 1,000 Americans, Cottonelle found that "overs" are more likely than "unders" to notice a roll's direction (74 percent), to be annoyed when the direction is incorrect (24 percent), and to have flipped the direction at a friend's home (27 percent).[53]

Besides orientation, toilet paper manufacturers and survey authors have studied other private practices around toilet paper: how much is used; whether it is torn off with one hand or two; whether it is torn off right-to-left or left-to-right; and whether it is crumpled or folded before use.[39]

Themes

Sex and age

Poretz and Sinrod break down the results of their 1989 survey by sex and age. These are the percentages of respondents who roll their paper over:[54]

Age
Sex
21–34 35–44 45–54 55 + Average
Male 71% 81% 60% 63% 69%
Female 81% 65% 62% 83% 67%
Average 76% 73% 61% 73% 68%

The book does not note the number of respondents in each segment, so it is difficult to say whether any of the deviations are statistically significant, but there does not seem to be a difference between men's and women's preferences. Nonetheless, such a difference has been claimed by other authors, in both directions. The American Standard conference poll concluded: "Many men voted for over, saying it made the paper easier to reach."[47] Inventor Curtis Batts arrives at a different conclusion from his personal experience: "Women like it over, and men like it under. I think it bugs women when it touches the wall."[55] Advice columnist Ms Maud of The Press asserts that women prefer over because they are "logical thinkers".[56]

A Cottonelle survey indicated that men were more likely than women to notice, and become annoyed with, a toilet roll hung against their preference.[57]

A popular-culture occurrence of a gender theory is found in the Weekly World News, a supermarket tabloid that runs outlandish stories for comedic effect. In the 2003 story North Korea Shocker!, the WWN claimed that North Korean leader Kim Jong-il was secretly female. As supporting evidence, Kim supposedly watched the Home Shopping Network, is a member of Oprah's Book Club, and "Yells at staffers who leave the toilet seat up and hang toilet paper rolls outward instead of inward."[58]

According to W. C. Privy's Original Bathroom Companion, Number 2, "By more than 4 to 1, older folks prefer to have their toilet paper dispense over the front."[59] The same claim is made by James Buckley's The Bathroom Companion for people older than 50.[60]

Class and politics

Sinrod observed of his survey, "60 percent of those who earn $50,000 or more prefer it to be over and 73 percent of those who earn less than $20,000 prefer under".[33] On what that proves: "I don't know, but it's sure interesting."[32]

In one local election in Saskatoon, Saskatchewan, new voting machines were given a trial run by asking the question, "Are you in favor of toilet paper in all public washrooms being installed with the loose end coming up and over the front of the roll?" The answer was yes: 768 to 196, or 80 percent over. It was thought to be a question "which carried no political association".[61] Yet one teenager's science project at the Southern Appalachian Science and Engineering Fair, and a favorite of the fair's coordinator, was a survey concluding that liberals roll over while conservatives roll under.[62]

Character

In his 2003 book 10 Steps to Sales Success, Tim Breithaupt proposes a set of four personality types evolving from Carl Jung's work: Socializer, Director, Thinker, and Relater. Breithaupt writes that toilet paper management is an important detail for Thinkers, while Directors don't care so long as the paper is available.[63] In her 2001 book Three Keys to Self-Understanding, Pat Wyman locates having an opinion on toilet paper hanging on the Enneagram of Personality, which classifies people as Ones, Twos, Threes, and so on: "Ones know the answer to such dilemmas."[64]

Noted preferences

Advice columnist Ann Landers (Eppie Lederer) was once asked which way toilet paper should hang. She answered under, prompting thousands of letters in protest; she then recommended over, prompting thousands more.[65] She reflected that the 15,000 letters made toilet paper the most controversial issue in her column's 31-year history,[66] wondering, "With so many problems in the world, why were thousands of people making an issue of tissue?"[65]

In November 1986, Landers told the Canadian Commercial Travellers Association that "Fine-quality toilet paper has designs that are right side up" in the over position.[66] In 1996, she explained the issue on The Oprah Winfrey Show, where 68 percent of the studio audience favored over; Oprah suggested that under uses more paper.[67] In 1998, she wrote that the issue "seems destined to go on forever", insisting, "In spite of the fact that an overwhelming number of people prefer the roll hung so that the paper comes over the top, I still prefer to have the paper hanging close to the wall."[61] On the day of her last column in 2002, Landers wrote, "P.S. The toilet paper hangs over the top."[68] Her published commentary on the issue has even continued after her death. 2005 saw the premiere of a one-woman play written by David Rambo: a character study of Ann Landers titled The Lady with All the Answers. Toilet paper comes up once again, and the actress surveys the audience for their opinions.[69]

In his article in Teaching Sociology, Burns writes that the toilet paper hanging exercise is valuable in part because "[the] subject matter is familiar to everybody; everyone is an expert, and everyone has an opinion."[70] Many entertainers, celebrities and businesspeople have publicized their opinion on the topic.

Seth Wheeler's original (c. 1891) U.S. Patent illustration.[71][72]

Social consequences

Toilet paper orientation is often mentioned as a hurdle for married couples.[73] The issue may also arise in businesses and public places.[74]

Even at the Amundsen–Scott Research Station at the South Pole, complaints have been raised over which way to install toilet paper. During the six-month-long polar night, a few dozen residents are stuck living together, and while many of the headaches of modern life are far away, food and hygiene are not. Despite the challenges posed by the hostile Antarctic climate, "It is in the more mundane trials of everyday life that personality clashes are revealed."[75]

Solutions

Some of the proposed solutions to this problem involve more or better technology, while others concentrate on human behavior.

Mechanical

Twelve rolls in a mixture of states

The Tilt-A-Roll is a swiveling toilet paper dispenser invented by Curtis Batts, a Dallas-native industrial engineer.[55] His patents on the invention published in 1996 and 1997, US 5588615  and US 5690302 , summarize its design, stating, "An adjustable angle coupling secures the yoke to the mounting assembly and permits rotation of the yoke about an axis directed orthogonally through the spindle such that the paper roll can be oriented to unroll paper either from over or from under the roll as desired."

Batts explains that his parents argued over toilet paper placement "all the time", as do he and his wife; the device's motto is "Let Tilt-A-Roll save your marriage!"[55] The Tilt-A-Roll has been featured on a variety of newspapers, magazines, radio interviews, and TV shows, including The Tonight Show with Jay Leno.[76] Batts entered the Tilt-A-Roll at the 1999 INPEX invention show, the world's largest invention show with 800 inventions,[77] and it won third place "for its appeal and simplicity".[78]

Batts started out constructing the devices in a workshop in his garage. He explains, "I've had a few sleepless nights where I went 24 hours making these things. I've got to find a manufacturer for it. I can't keep up with the volume."[55] As of 2000, Batts was still "in the process of selecting a distributor";[79] he has tried The Home Depot[76] and QVC.[80] As of 2008, the Tilt-A-Roll is on sale at Batt's website.[81]

An inventor named Rocky Hutson demonstrated a similar device he called the T.P. Swivel to the producers of the television program PitchMen in late 2009. Of 173 entrants gathered at Ybor City, Tampa, Florida, Hutson was one of the twenty chosen to pitch their products to Anthony Sullivan.[82] For his part, Hutson pulls his paper from the top of the roll.[83]

Another solution: install two toilet paper dispensers, as is more common in public restrooms and hotels.[84] A reader of the Annie's Mailbox column recommends using a holder large enough to fit two rolls, noting that the roll mounted over is more popular. Another reader sidesteps the issue by foregoing the holder, instead piling five or six rolls in a big wicker basket.[85] Even using separate bathrooms can help.[86] Other solutions include vertical holders.

Behavioral

A Grand Rapids, Michigan, toilet paper enthusiast named Bill Jarrett argues that previous polls have been too small. He wants a national referendum with at least one million votes, with the result to decide a "national toilet paper hanging way" to be enforced by "the toilet paper police".[87] Jarrett refuses to reveal his own preference; he even removed the toilet paper from his house's bathrooms before inviting in an AP reporter for an interview. "I'm not saying because I don't want to influence the vote."[88] Voting requires the purchase of a $5 debate kit. His value proposition to the nation: assuming that one can spend half an hour per year searching for the end of the toilet paper, the United States should save 90 million hours at home per year—and $300 million at the workplace.[89]

Toilet paper orientation has been used rhetorically as the ultimate issue that government has no business dictating, in letters to the editor protesting the regulation of noise pollution[90] and stricter requirements to get a divorce.[91] In 2006, protesting New Hampshire's ban on smoking in restaurants and bars, representative Ralph Boehm (RLitchfield) asked "Will we soon be told which direction the toilet paper must hang from the roll?"[92]

David O'Connor's 2005 book Henderson's House Rules: The Official Guide to Replacing the Toilet Paper and Other Domestic Topics of Great Dispute aims to solve disagreements with a minimum of debate or compromise by offering authoritative, reasonable rules.[93] The "House Rule" for toilet paper is over and out, and a full page is dedicated to a diagram of this orientation. But O'Connor writes that "if a female household member has a strong preference for the toilet paper to hang over and in, against the wall, that preference prevails. It is admittedly an odd preference, but women use toilet paper far more often than men—hence the rule."[94]

Notes and references

Notes

  1. This paragraph summarizes material in the body; details and citations are found below. For definitions of the choices, see Preliminaries. Habit is discussed in Arguments. See Survey results for statistics.
  2. For pros and cons, including RVs and cats, see Arguments; for celebrities and experts, including Ann Landers, see Noted preferences; for theories, see Themes.
  3. The enthusiast, Bill Jarrett, and the inventor, Curtis Batts, are described in Solutions.
  4. Burns 2003.
  5. Burns 2003, p. 111.
  6. Burns 2003, p. 113.
  7. Collett 2008.
  8. Paul 2006. The previous topics are discussed in the section "Finding Sociology in everyday places: a review".
  9. Peterson 2006, pp. 173–175.
  10. Gernsbacher 2007.
  11. Cesvet, Babinski & Alper 2008, p. 68.
  12. Voice of America 2004.
  13. 1 2 Progressive Grocer 2010.
  14. Ode 2010: "The Kimberly-Clark company cites three advantages for rolling over: perforation control, viewing advantage and wall avoidance."; Garton 2005; Jarski & Jarski 2007.
  15. Ode 2010; Elliott 2006
  16. Lind 1992; "The Grand Princess cruise ship replaces its toilet paper with the leading edge over the front, so that it can be folded as is done in five-star hotels. (Yes, someone really did ask this question.)" (Carpenter 1999); Rosencrans 1998; Garton 2005.
  17. Grant 1991b; Garton 2005; Mitchell & Sugar 2005a; Jarski & Jarski 2007.
  18. Jarski & Jarski 2007
  19. Brandweek 2009
  20. Darbo 2007; Garton 2005; O'Connor 2005, p. 63.
  21. Nerbas 2009.
  22. Ode 2010; Weingarten 2008; Keeran 1993.
  23. Downey & Harrison 1993.
  24. McNatt 2010.
  25. Centralian Advocate 2002.
  26. Yeld 2010.
  27. FitzSimons 2009, p. 99.
  28. Scriven 1991, "EVALUATION SKILLS", pp. 151–153, especially p. 153 for the quotations.
  29. Nalebuff & Ayres 2006, pp. 115–118.
  30. Harris 2010.
  31. The Daily Examiner 2009.
  32. 1 2 Rubin 1989.
  33. 1 2 Oldenburg 1989.
  34. Mark Wolf Scripps Howard News Service 1990.
  35. Kanner 1995, pp. 56, 120.
  36. Ladan 2001.
  37. Nestruck 2005.
  38. The 1996 report, which may not have contained this question, was the fourth annual report: (McCarthey 1996)
  39. 1 2 PR Newswire 1993.
  40. 1 2 Ortega 1995.
  41. Ciancio 1994.
  42. Ciancio 1995.
  43. Dickson 2001.
  44. Ebenkamp 2004; Pierson 2004.
  45. 1 2 Toronto Star staff and news services 1993.
  46. Stark 1993.
  47. 1 2 Clark 1993.
  48. American Standard Press 2008.
  49. Harden 1995.
  50. Henry 1999.
  51. CottonelleRollPoll.com
  52. Ode 2010.
  53. PR Newswire 2010.
  54. Poretz & Sinrod 1989, p. 34.
  55. 1 2 3 4 Floyd 1999.
  56. Ms Maud 2002.
  57. Kimberly-Clark 2010.
  58. LaForte 2003.
  59. Barrett & Mingo 2003, p. 400.
  60. Buckley 2005, p. 106.
  61. 1 2 Landers 1998.
  62. Keim 1997.
  63. Breithaupt 2003, pp. 126, 135.
  64. Wyman 2001, p. 61.
  65. 1 2 Marelius 1987.
  66. 1 2 Toronto Star 1986.
  67. The Oprah Winfrey Show 1996.
  68. Landers 2002.
  69. Welsh 2005; Rawson 2008.
  70. Burns 2003, p. 116.
  71. Maybelle Morgan (19 March 2015). "Over or under? The age-old debate of which way a roll of toilet paper should sit is FINALLY settled... by a 124-year-old diagram". Mailonline, dailymail.co.uk. Daily Mail. Retrieved 2 May 2015.
  72. Jenny Che (17–19 March 2015). "This 124-Year-Old Patent Reveals The Right Way To Use Toilet Paper". HuffPost: Business. The Huffington Post. Retrieved 2 May 2015.
  73. Wolf 1999, pp. 74–75; Hogan & Hogan 2000, p. 200.
  74. Lui 2009; Grant 1991a.
  75. Daily Express 1999, p. 39.
  76. 1 2 Newman 2000.
  77. Miller 1999.
  78. Greenberg 2007, p. 149.
  79. Hunt & Edwards 2000.
  80. Stovall 1997.
  81. Greenberg 2007, p. 149. See The Tilt-A-Roll homepage at Curtis Batts Online
  82. Zayas 2009.
  83. Luna 2009.
  84. Walsh 1999; Marelius 1987.
  85. Mitchell & Sugar 2005b.
  86. Arkins 1994; Jarski & Jarski 2007.
  87. Godfrey 2006, p. 103.
  88. Rademacher 2005.
  89. Lind 1992.
  90. Ratzlaff 2009.
  91. Wuthrich 2006.
  92. Saunders 2006.
  93. O'Connor 2005, pp. 2–3.
  94. O'Connor 2005, pp. 63–64; Davis 2006.

References

Further reading

  • "For Your Information", The News & Observer, p. C1, 4 October 1993, Factiva rnob000020011101dpa400p2p 
    References "a Reader's Digest poll". Primary source unclear.
  • Brody, Ed (2002), Spinning Tales, Weaving Hope: Stories, Storytelling, and Activities for Peace, Justice and the Environment, New Society Publishers, p. 158 
  • Cameron, W. Bruce (2004), How to Remodel a Man: Tips and Techniques on Accomplishing Something You Know Is Impossible But Want to Try Anyway, Macmillan, p. 185 
  • Carpenter, Richard P. (28 March 1999), "It's swimming vs. snoozing", The Boston Globe, p. M4, Factiva bstngb0020010825dv3s00asy 
  • Freeman, Kim (8 February 1986), "Vox Jox", Billboard, p. 16 
    References a poll by Ric Hanson featured in USA Today.
  • Grossvogel, David I. (1987), Dear Ann Landers: our intimate and changing dialogue with America's best-loved confidante, Contemporary Books, p. 257 
  • Kelly, William Jude (1988), Models in process: a rhetoric and reader, Macmillan, p. 154 
  • Kogan, Rick (2004), America's Mom: The Life, Lessons, and Legacy of Ann Landers, Thorndike Press, p. 224 
  • Praeger, Dave (2007), Poop Culture: How America Is Shaped by Its Grossest National Product, Feral House, p. 72 
  • Selby, David (1995), Earthkind: a teachers' handbook on humane education, Trentham Books, p. 367 
  • Singular, Stephen (1987), Talked to death: the life and murder of Alan Berg, p. 305 
    Mentions Bob Palmer of Denver's KCNC-TV doing a show on this topic.
  • Society of Automotive Engineers (2004), Reliability and robust design in automotive engineering, p. 412 
    Presents a statistical test to determine gender differences in toilet paper orientation.
  • Trachtenberg, Robert (2005), When I Knew, HarperCollins, p. 69 
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