Preliminary Data Indicating a Relationship Between Primary Nocturnal Enuresis and Handedness
 
 

by Mark A. Murphy
copyright 2000, Mark A. Murphy
(Research initiated November 1998, originally submitted December 4, 2000 to "Pedriatrics" medical journal, not accepted.  Submitted August 16, 2001 to the "Journal of Paediatrics and Child Health", awaiting review)
(this version is a draft, comments welcome, please send to murphy@tarleton.edu)

Abstract

     A survey of college students indicates a significant relationship between the manifestations of monosymptomatic primary nocturnal enuresis and left-handedness.  There was no significant relationship between sex and handedness, and only a marginal relationship between sex and enuresis, with males being more prone to enuresis at just under the p= 0.05 level.  The significance of the relationship between enuresis and handedness, in conjunction with a review of the literature, indicates that there is a possibility that both conditions may share at least one genetic origin.  Preliminary data is presented to support this argument with a short discussion of previous research into both areas.

Introduction

     Left-handedness has been associated with many physical and mental conditions including shortened lifespan and sleep apnea (Hoffstein, 1993), Attention Deficit Disorder (Comings & Comings 1987), cognitive deficits in development of Alzheimer’s disease (Doody, et al, 1999), and homosexuality (Bailey, 1999).  In addition to being more likely to die younger, left-handers have higher injury rates in sports, at home and work, and while driving (U.S. News & World Report, 1993).  There is a definite decline of left-handedness with increased age (Stellman, et al, 1997).  Aside from being associated with shorter lifespan, this decline may be due, in part, to social pressure to change handedness in order to conform to the right-handed norm, a situation not as strictly enforced in the West today (Klar, 1996).
     It is estimated that 5-7 million children in the United States suffer from primary nocturnal enuresis (PNE) (Cendron, 1999), the most common form of bedwetting (von Gontard, et al, 1997).  While no discussion or study of a direct relationship between left-handedness and nighttime bed wetting was found, there appeared to be a sufficient amount of anecdotal evidence, concurrent manifestations, and literature on shared phenotypical traits to warrant formation of the hypothesis that they are related, and to conduct tests of that hypothesis.
     The concept for this study began as anecdotal evidence pointing to a relationship between PNE and left handedness.  The author was seeking medical treatment advice for an 8-year-old son who suffered from nightly bedwetting episodes.  The author has a brother who is left-handed and had pre-pubescent enuresis, and the author’s spouse had a sister who was a left-handed enuretic.  Since the son was left-handed, the author asked the physician treating the boy if there was possibly a genetic link or correlation between the two.  The physician said he had never heard of a link, but that he so happened to be left-handed and was enuretic prior to puberty as well.  This started a concept that was perpetuated by the fact that when the author sought advice or potential partner with a medical background for a preliminary study on the correlation, the first person consulted also responded that she was a left-handed sufferer of PNE.  As Coren (1993) has said, “Serendipity plays a role in science”.
     The purpose of this study was to collect preliminary data to support or refute the hypothesis that an actual relationship exists between left-handedness and monosymptomatic PNE, not to provide genetic or cultural models, nor to further any school of thought as to origins of PNE and handedness.  A small, introductory discussion of the genetic vs. cultural origin controversy is presented, but to understand the arguments in depth, a detailed review of over 70 years of research literature is required, which is beyond the scope of this preliminary study.  Sources for various, detailed studies of genetics, handedness and PNE are referenced.
     Monosymptomatic PNE is the onset or continuation of consistent bedwetting after age 5 and up to age 15.  These patients exhibit no obvious physiological reason for PNE, such as reduced bladder capacity (Johnson, 1998).  Patients with obstructive sleep apnea (OSA) are shown to have increased urine output at night due to level increases of the hormone atrial natriuretic peptide (ANP), which may play a role in PNE in children (Krieger, 1995).  PNE also has been associated with a decreased nighttime secretion of antidiuretic hormone (Cendron, 1999).  While children with secondary nocturnal enuresis (that which is caused by a pathology) often exhibit behavioral disorders and psychosocial stress, those with PNE are usually better socially adjusted (von Gontard, et al, 1998).  By the age of 5, the bladder should be in a relatively mature state and the child should be exhibiting adult pattern urinary control (Johnson, 1998).  About 11% of children between the ages of 5 and 17 report bed-wetting at least once in the previous year.  Boys have a slight tendency to wet more than girls (Byrd & Weitzman, 1996).
     Approximately 90% of the population are right-handed (Corballis, 1997, U.S. News & World Report, 1993).  Animals show almost an even preference for right and left side dominance, with the exception of great apes which are about 2:1 right to left “handed” (Corballis, 1997), while humans uniquely prefer the right (Bello, 1986).  The ratio of left-handed men to left-handed women has been described at about 3:1 (U.S. News & World Report, 1993), but Cerone & McKeever (1999) indicate no hand preference class by sex interaction.  The male to female ratio for PNE sufferers is also 3:1 (Arnell, et al, 1997), perhaps coincidentally.  Perinatal exposure to testosterone appears to have an effect on handedness, but it is not clear if neonatal or prenatal exposure has the most effect (Clark, et al, 1996; Coren, 1998).  Handedness has been associated with faster maturational development of the left cerebral hemisphere (Gabbard, 1995), and cerebral dominance (Annett, 1964; Corballis, 1997), but hand preference seems to have no relationship to cognitive ability in developed individuals (Cerone & McKeever, 1999).
     There are several definitions of handedness and ways to determine sidedness, laterality or sinistrality, including indices created by various researchers using a wide variety of tests and motor skill evaluations (Klar 1996, Coren & Searleman 1987, French & Richards 1990, Annette 1964).  With the use of questionnaires in handedness studies, it has been shown that no particular bias due to anxiety by left-handers will contaminate the results (Beaton & Moseley, 1991; French & Richards, 1990).  In the present study respondents were surveyed as to whether they considered themselves left-handed or not.  Some bias may be possible in older respondents especially because of former school trends and attitudes that forced conformation to right-handedness.  Today's attitudes are more culturally accepting of left-handedness (Klar, 1996).  However, the social and cultural pressures associated with PNE may present a different problem.
     Genetic causes and phenotypical manifestations of handedness and PNE have been studied, but always separately.  The closest study found containing both, though not necessarily in concert, revealed that enuresis is present in 19-36% of Tourette Syndrome patients, and that 30-35% of Tourette Syndrome patients were left-handed (Comings & Comings, 1987). The candidate gene or genes responsible for enuresis have been likely identified, specifically assigned to chromosomes 13q, probably 12q (Eiberg, 1995a; Arnell, et al, 1997), and possibly 8q (von Gontard, et al, 1997; Hollmann, et al, 1998).  The genetic locus of mutation resulting in an allele for handedness is believed to have arisen as a characteristic of Homo sapiens development about 200,000 years ago.  This could have been the result of the development of an opposable thumb, but may have been a result of the ability to create speech by lateralizing brain communication centers (Corballis, 1997).  Archaeology has shown 5000-year-old cave paintings, use of paleolithic tools and Cro-Magnon man studies also display the 90% right hand tendencies of humans (Bello, 1986, Corballis, 1997).
     The simple Mendelian model does not hold for a handedness gene at a single locus (Corballis, 1997).  However, despite conflicting twin studies, definite familial patterns have emerged with respect to handedness as evidenced by the legendary Kerr family of Scotland.  In the Middle ages, “Kerr-handed” people carried shields in the right hand, swords in the left, thus making it more likely to take a fatal blow to the heart.  Kerr castle staircases wound up in a counter-clockwise spiral to give them the edge in a sword fight.  More recent studies of the Kerr clan show about 30% left-handers compared to about 10% in the general population (Coren, 1993).  Annett (1996), Klar (1996) and others have presented a model for a single gene that controls handedness.  They specify that this gene/locus actually specifies cerebral laterality and that individuals lacking this gene have a 50% chance of being left-handed.
     Hollmann, et al (1998) also state that PNE has been shown to be familial in nature, but that there has been no statistically significant association between linkage to a chromosome interval and type of enuresis.  More than 50% of PNE may be familial (Super & Postlethwaite, 1997).  It has been suggested that recessive genes code for handedness, but recent analyses of larger families indicate an autosomal dominant inheritance with high penetrance, which may be influenced by other genes and environmental factors (Norgaard, et al, 1997).  One gene that controls the likelihood of handedness may be located on chromosome 12 (Eiberg, 1995b).  It is not likely that the gene or genes are located on the sex chromosome, but genes located there may influence handedness or cerebral asymmetry (Corballis, 1997).
     Some researchers believe that exact searches for candidate genes of PNE on chromosomes 12q and 13q should concentrate on those areas associated with sleep abnormalities (Super & Postlethwaite, 1997).  PNE sufferers have higher incidences of defective sleep arousal mechanisms (Neveus, et al 1999) and sleep-related breathing disorders (Messner, 1999), while older children with PNE are more difficult to rouse from sleep than younger sufferers (Super & Postlethwaite, 1997).  Arousal response to bladder distension develops with age (Watanabe, 1995).  Left-sided people also have greater occurrences of sleep disturbances (Coren & Searleman, 1987).  Surprisingly, left-handedness also appears associated with severe sleep apnea or obstructive sleep apnea (OSA), which may help to explain a higher mortality rate amongst left-handed people (Hoffstein, 1993).  Enuresis, though an unusual symptom in adult OSA, is a classic symptom of childhood OSA (Kramer, et al, 1998).   In fact, certain types of secondary enuresis are resolved with surgical treatment of OSA, but this is not true of PNE (Wang & Vordemark, 1994).

Method

     The primary data-gathering mechanism was the use of a survey of 168 university students at Tarleton State University, all respondents in a voluntary and anonymous exercise.  A college student population was chosen for this survey because it was surmised that most would be of a post-pubescent age, possibly old enough to overcome some of the emotional trauma associated with PNE, yet young enough to clearly remember wetting the bed and remember siblings who did the same.  In one category, numbers of siblings and their statistics were used with the same weight as the conditions of the primary respondents.  Also at this approximate age level there should be less bias due to social pressures of switching handedness (Klar, 1996) and a general decline of left handedness with increased age (Stellman, et al 1997, Coren 1993).   Preliminary interviews of left handed persons for this study who were older than about 35 indicated that many had forgotten whether or not they wet the bed between 5 and 15 years of age, and several failed to recall if any siblings did as well.
     Observations were grouped into different categories for comparison, the main comparison being the handedness of the survey respondent to the manifestation of monosymptomatic primary nocturnal enuresis (table A).  A slight modification of this comparison included those listed as ambidextrous to be left-handed (table B).  Studies have included ambidextrous individuals as left-handed (Klar, 1996.)  Another category included the summed data from both the respondents directly and the information provided by them on their siblings (table C).  Other comparisons were made of sex to PNE (table D) and sex to handedness (table E).
     Chi-square analyses of two by two tables were used to analyze the data of each category.  Probability based on the chi-square determination was calculated at the 95% (p=0.05) confidence level, with some comparisons at other levels (see tables).  Handedness has been associated with disease and disease risk factors  (Stellman, et al, 1997) and comparisons have been made of left handedness to sleep disorders (Hoffstein, 1993), both with the use of chi-square analysis.  Neveus, et al (1999) used chi-square for simple comparisons of sex, enuresis and sleep disorders.  Szeszko, et al (1997) determined no significant difference between gifted and non-gifted children in distribution of left and right handed writing with the use of chi square comparison.
     The following questions were asked on the survey: What is your sex?  What is your age? (grouped 18-25, 26-35, 36-49, 50-65, over 65).  Are you left, right or both-handed?  How many of your siblings are/were left handed?  How many of your siblings are/were right-handed?  Did you wet the bed between the ages of 5 and 15?  How many of your right-handed siblings experienced bed wetting after age 5 but before age 15?  How many of your left-handed siblings experienced bed wetting after age 5 but before age 15?  Answers were tabulated and totaled with chi-square analysis performed for the different categories as mentioned.

Results

     The number of respondents totaled 168.  Age category totals were as follows: 99 respondents were 18-25 years old, 37 were 26-35, 27 were 36-49, 4 were 50-65, and 1 was over 65.  Of these, 131 considered themselves right-handed, 32 left-handed and 5 both-handed.  Those who answered affirmative to bed wetting between the ages of 5 and 15 were 34, while 134 responded in the negative.  Males totaled 43 and females totaled 125, which may have been skewed due to the majority of participants apparently being nursing students, though an effort was made to distribute the survey campus-wide.  See the attached tables for other totals, relationships and descriptive chi-square analyses of those relationships.
     At the 95% confidence level, a significant relationship was seen between being left-handed and suffering from PNE.  This was true in both the respondent data excluding ambidextry, the respondent data including ambidextry, and the respondent plus sibling data including ambidextry.  The respondent data set excluding ambidexterity neared the 97.5% confidence level.  The respondent plus sibling data showed a significant relationship through the 99.9% confidence level, possibly because this was a larger population of individuals.  The relationship between sex and PNE, though not significant (at p= 0.05) was closer to the 95% level than to the 90% level.  No relationship at all could be determined for sex and handedness with this data set.  Age was not taken into account, nor was the effect of familial sibling relationship to probability, though enuresis has been found to be more often a shared sibling trait (Hollmann, et al, 1998).

Discussion

     Based on this preliminary survey data, it appears that there is a significant relationship between handedness and PNE.  Combined with current literature and studies, the possibility is presented that PNE and handedness may have some genetic connection.  No significant relationship can be shown for sex and PNE, or for sex and handedness, with this data set.  Future studies need to be performed, with a larger population and possibly with a more defined classification of handedness using one of several accepted indices.  It is suggested that clinical data is needed on PNE patient populations to further or contest the hypothesis.
     Some anxiety of enuretic sufferers could have contributed to a bias of the study, though the surveys were completely anonymous.  No anxiety bias on the questionnaires was expected due to handedness (Beaton & Moseley, 1991; French & Richards, 1990).  Another possible bias contributor was the subjective description of PNE in the survey, especially when using data based on memory of sibling characteristics.  No bias determination of the effects of age, or the relationship of handedness and enuresis between siblings was attempted.  Some anecdotal evidence suggests that males participants may have a harder time admitting to having certain conditions, such as enuresis, as compared with females.  This must also be considered as a possible bias in future studies.

Acknowledgements

 Special thanks to Diana Kunce, R.N., Dok Woods, R.N. and the Tarleton State University Nursing Department for assisting in dissemination and collection of the surveys.  Thanks to Bobby Donohue, M.D., John Calahan, Ph.D. and Nancy Easterling for reviews and comments on this paper.

---

References 1. Annett, M. 1964.  A Model of the Inheritance of Handedness and Cerebral Dominance, Nature, Vol. 204, pp. 59-60.
2. Annett, M., 1996.  In Defense of the Right Shift Theory, Perpetual and Motor Skills, Vol. 82, pp. 115-137.
3. Arnell, H., K. Hjalmas, M. Jagervall, G. Lackgren, A. Stenberg, B. Bengtsson, C. Wassen, T. Emahazion, G. Anneren, U. Pettersson, M. Sundvall, N. Dahl, 1997.  The genetics of primary nocturnal enuresis: inheritance and suggestion of a second major gene on chromosome 12q, Journal of Medical Genetics, Vol. 34, pp. 360-365.
4. Bailey, J. M., 1999. Homosexuality and Mental Illness, Archives of General Psychiatry, Vol. 56, October, pp. 883-884.
5. Bello, M., 1986.  What causes left-handedness, Science, Vol. 7, p. 83.
6. Beaton, A.A. and L.G. Moseley, 1991.  Hand preference scores and completion of questionnaires: Another look, British Journal of Psychology, Vol. 82, Issue 4, p. 521.
7. Byrd, R.S. and M. Weitzman, 1996.  Bed-wetting in U.S. children: Epidemiology and related behavior problems, Pediatrics, Vol. 98, No. 3, September, pp. 414-420.
8. Cendron, M., 1999.  Primary Nocturnal Enuresis: Current Concepts, American Family Physician, March 1, 1999.
9. Cerone, L.J. and W.F. McKeever, 1999.  Failure to support the right-shift theory’s hypothesis of a ‘heterozygote advantage’ for cognitive abilities, British Journal of Psychology, Vol. 90, pp. 109-123.
10. Clark, M.M., R.K. Robertson, and B.G. Galef, Jr., 1996.  Effects of Perinatal Testosterone on Handedness of Gerbils: Support for Part of the Geschwind-Galaburda Hypothesis, Behavioral Neuroscience, Vol. 110, No. 2, 413-417.
11. Comings, D.E., and B.G. Comings, 1987.  A Controlled Study of Tourette Syndrome, VI, Early Development, Sleep Problems, Allergies, and Handedness, American Journal of Human Genetics, Vol. 41, pp. 822-838.
12. Corballis, M.C., 1997.  The Genetics and Evolution of Handedness, Psychological Review, Vol. 104, No. 4, 714-727.
13. Coren, S. and J. Searleman, 1987.  Left Sidedness and Sleep Difficulty: The Alinormal Syndrome, Brain and Cognition, Vol. 6, pp. 184-192.
14. Coren, S., 1998.  Prenatal testosterone exposure, left handedness, and high school delinquency, Behavioral and Brain Sciences, Vol. 21, No. 3, Commentary, pp. 369-370.
15. Coren, S., 1993.  Left Hander, John Murray Publishers, Ltd., London, England.
16. Doody, R.S., J.L. Vacca, P.J. Massman, T. Liao, 1999.  The Influence of Handedness on the Clinical Presentation and Neuropsychology of Alzheimer Disease, Archives of Neurology, Vol. 56, Sept., pp. 1133-1137.
17. Eiberg, H., I. Berendt and J. Mohr, 1995(a).  Assignment of dominant inherited nocturnal enuresis (ENUR1) to chromosome 13q, Nature Genetics, Vol. 10, pp. 354-356.
18. Eiberg, H., 1995(b).  Nocturnal enuresis is linked to a specific gene, Scandinavian Journal of Urology and Nephrology, Supplement 173, pp. 15-18.
19. French, C.C. and A. Richards, 1990.  The relationship between handedness, anxiety and questionnaire response patterns, British Journal of Psychology, Vol. 81, February, Issue 1, p. 57.
20. Gabbard, C. and S. Hart, 1995.  General motor proficiency and handedness in children, Journal of Genetic Psychology, Vol. 156, No. 4, December, p. 411.
21. Ball, C.N and J. Connor-Linton, Web Chi Square Calculator, Georgetown University, 1999, http://www.georgetown.edu/cball/webtools/web_chi.html.
22. Hoffstein, V., C. K. Chan, and A. S. Slutsky, 1993.  Handedness and Sleep Apnea, Chest, Vol. 103, No. 6, pp. 1860-1862.
23. Hollmann, E., A. von Gontard, H. Eiberg, S. Rittig, and G. Lehmkuhl, 1998.  Molecular genetic, clinical and psychiatric associations in nocturnal enuresis, British Journal of Urology, Vol. 81, Supplement 3, pp. 37-39.
24. Johnson, M., 1998.  Nocturnal Enuresis, Urologic Nursing, Vol. 18, No. 4, pp. 259-273.
25. Klar, A. J., 1996.  A single locus, RGHT, specifies preference for hand utilization in humans, Cold Spring Harbor Symposium on Quantitative Biology LXI, pp. 59-65.
26. Kramer, N.R., A.E. Bonitati, and R.P. Millman, 1998.  Enuresis and obstructive sleep apnea in adults, Chest, Vol. 114, No. 2, pp. 634-638.
27. Krieger, J., 1995.  Hormonal control of sodium and water excretion in obstructive sleep apnoea, Scandinavian Journal of Urology and Nephrology, Supplement 173, pp. 65-69.
28. Messner, Anna H., 1999.  Evaluation of Obstructive Sleep Apnea by Polysomnography Prior to Pediatric Adenotonsillectomy, Arch. Otolaryngology-Head and Neck Surgery, Vol. 125, March, pp. 353-356.
29. Neveus, T., J. Hetta, S. Cnattingius, T. Tuvemo, G. Lackgren, U. Olsson, and A. Stenberg, 1999.  Depth of sleep and sleep habits among enuretic and incontinent children, Acta Paediatrica, Vol. 88, pp. 748-752.
30. Norgaard, J.P., J.C. Djurhuus, H. Watanabe, A. Stenberg, and B. Lettgen, 1997.  Experience and current status of research into the pathophysiology of nocturnal enuresis, British Journal of Urology, Vol. 79, pp. 825-835.
31. Stellman, S. D., E. L. Wynder, D. J. DeRose, and J. E. Muscat, 1997.  The Epidemiology of Left-Handedness in a Hospital Population, Annals of Epidemiology, Vol. 7, pp. 167-171.
32. Szeszko, P. R., G. M. Madden, and J. M. Piro, 1997.  Factor Analyses of Handedness Items in Left and Right-Handed Intellectually Gifted and Nongifted Children, Cortex, Vol. 33, pp. 579-584.
33. Super, M. and R.J. Postlethwaite, 1997.  Genes, familial enuresis, and clinical management, Lancet, Vol. 350, No. 9072, September 19th, pp. 159-160.
34. U.S. News & World Report, 1993.  Database, Left and Right Handedness, U.S. News & World Report, August 9, Vol. 115, No. 6, p. 14-20.
35. von Gontard, A., E. Hollmann, H. Eiberg, B. Benden, S. Rittig, and G. Lehmkuhl, 1997.  Clinical enuresis phenotypes in familial nocturnal enuresis, Scandinavian Journal of Urology and Nephrology, Vol. 183, Supplement, pp. 11-16.
36. von Gontard, A., H. Eiberg, E. Hollmann, S. Rittig, and G. Lehmkuhl, 1998.  Molecular genetics of nocturnal enuresis: clinical and genetic heterogeneity, Acta Paediatrica, Vol. 87, pp. 571-578.
37. Wang, R.C. and J. Vordemark, 1994.  Effects of Sleep Apnea Treatment Upon Enuresis in Children, Surgical Forum, Chapter 13- Otorhinolaryngology, pp. 643-644.
38. Watanabe, H., 1995. Sleep patterns in children with nocturnal enuresis, Scandinavian Journal of Urology and Nephrology, Supplement 173, pp. 55-57.

---

 Table A

Chi Square Comparison of Handedness to PNE
(Respondent only, ambidextrous removed)

 Left Right Totals
Wet 11 22 33
Dry 21 109 130
Totals 32 131 163
 

Table A Analysis

Degrees of freedom (df) = (rows - 1) x (columns - 1)
      df = (2-1) x (2-1) = 1
Expected frequencies for each cell
Row 1 Column 1
Observed value (O) = 11
Expected value (E) = (row total x column total) / grand total
E = (33 x 32) / 163 = 6.47852760736196
Chi-square = (O - E)squared / E
Chi-square = ((11 - 6.47852760736196) **2) / 6.47852760736196
Chi-square = 3.1556109406953
Total chi-square now = 3.1556109406953
Row 1 column 2
Observed value (O) = 22
Expected value (E) = (row total x column total) / grand total
E = (33 x 131) / 163 = 26.521472392638
Chi-square = (O - E)squared / E
Chi-square = ((22 - 26.521472392638) **2) / 26.521472392638
Chi-square = 0.770836260322515
Total chi-square now = 3.92644720101781
Row 2 column 1
Observed value (O) = 21
Expected value (E) = (row total x column total) / grand total
E = (130 x 32) / 163 = 25.521472392638
Chi-square = (O - E)squared / E
Chi-square = ((21 - 25.521472392638) **2) / 25.521472392638
Chi-square = 0.801039700330344
Total chi-square now = 4.72748690134816
 Table A Analysis (cont.)

Row 2 column 2
Observed value (O) = 109
Expected value (E) = (row total x column total) / grand total
E = (130 x 131) / 163 = 104.478527607362
Chi-square = (O - E)squared / E
Chi-square = ((109 - 104.478527607362) **2) / 104.478527607362
Chi-square = 0.195673819928023
Total chi-square now = 4.92316072127618
Probability (P):
Critical values for chi at df = 1:

Sig levels 0.20 0.10 0.05 0.025 0.01 0.001
Crit value 1.64 2.71 3.84 5.02 6.64 10.83
 

Sig. 0.20: chi is greater than or equal to 1.64
Sig. 0.10: chi is greater than or equal to 2.71
Sig. 0.05: chi is greater than or equal to 3.84
Degrees of freedom: 1
Chi-square = 4.92316072127618
p is less than or equal to 0.05.
The distribution is significant.

---

 Table B: Chi Square Comparison of Handedness to PNE
(Respondent only, ambidextrous included as left-handed)

 Left Right totals
Wet 12 22 34
Dry 25 109 134
totals 37 131 168
 

Table B Analysis

Degrees of freedom (df) = (rows - 1) x (columns - 1)
df = (2-1) x (2-1) = 1
Expected frequencies for each cell:
Row 1 column 1
Observed value (O) = 12
Expected value (E) = (row total x column total) / grand total
E = (34 x 37) / 168 = 7.48809523809524
Chi-square = (O - E)squared / E
Chi-square = ((12 - 7.48809523809524) **2) / 7.48809523809524
Chi-square = 2.71861988038459
Total chi-square now = 2.71861988038459
Row 1 column 2
Observed value (O) = 22
Expected value (E) = (row total x column total) / grand total
E = (34 x 131) / 168 = 26.5119047619048
Chi-square = (O - E)squared / E
Chi-square = ((22 - 26.5119047619048) **2) / 26.5119047619048
Chi-square = 0.767854470032288
Total chi-square now = 3.48647435041687
Row 2 column 1
Observed value (O) = 25
Expected value (E) = (row total x column total) / grand total
E = (134 x 37) / 168 = 29.5119047619048
Chi-square = (O - E)squared / E
Chi-square = ((25 - 29.5119047619048) **2) / 29.5119047619048
Chi-square = 0.689799074127433
Total chi-square now = 4.17627342454431
Row 2 column 2
Observed value (O) = 109
Expected value (E) = (row total x column total) / grand total
 Table B Analysis (cont.)

E = (134 x 131) / 168 = 104.488095238095
Chi-square = (O - E)squared / E
Chi-square = ((109 - 104.488095238095) **2) / 104.488095238095
Chi-square = 0.194828746127595
Total chi-square now = 4.3711021706719
Probability (P):
Critical values for chi at df = 1:

Sig levels 0.20 0.10 0.05 0.025 0.01 0.001
Crit value 1.64 2.71 3.84 5.02 6.64 10.83

Sig. 0.20: chi is greater than or equal to 1.64
Sig. 0.10: chi is greater than or equal to 2.71
Sig. 0.05: chi is greater than or equal to 3.84
Degrees of freedom: 1
Chi-square = 4.3711021706719
p is less than or equal to 0.05.
The distribution is significant.

---

Table C: Chi Square Comparison of Respondent and Sibling Handedness vs. PNE

 Left Right totals
Wet 28 63 91
Dry 67 403 470
totals 95 466 561
 

Table C Analysis

Degrees of freedom (df) = (rows - 1) x (columns - 1)
df = (2-1) x (2-1) = 1
Expected frequencies for each cell:
Row 1 column 1 ...
Observed value (O) = 28
Expected value (E) = (row total x column total) / grand total
E = (91 x 95) / 561 = 15.4099821746881
Chi-square = (O - E)squared / E
Chi-square = ((28 - 15.4099821746881) **2) / 15.4099821746881
Chi-square = 10.2860955350119
Total chi-square now = 10.2860955350119
Row 1 column 2
Observed value (O) = 63
Expected value (E) = (row total x column total) / grand total
E = (91 x 466) / 561 = 75.5900178253119
Chi-square = (O - E)squared / E
Chi-square = ((63 - 75.5900178253119) **2) / 75.5900178253119
Chi-square = 2.09695080649385
Total chi-square now = 12.3830463415058
Row 2 column 1
Observed value (O) = 67
Expected value (E) = (row total x column total) / grand total
E = (470 x 95) / 561 = 79.5900178253119
Chi-square = (O - E)squared / E
Chi-square = ((67 - 79.5900178253119) **2) / 79.5900178253119
Chi-square = 1.99156317805551
Total chi-square now = 14.3746095195613
Row 2 column 2
Observed value (O) = 403
Expected value (E) = (row total x column total) / grand total
E = (470 x 466) / 561 = 390.409982174688
 Table C Analysis (cont.)

Chi-square = (O - E)squared / E
Chi-square = ((403 - 390.409982174688) **2) / 390.409982174688
Chi-square = 0.406005368916893
Total chi-square now = 14.7806148884782
Probability (P):
Critical values for chi at df = 1:

Sig levels 0.20 0.10 0.05 0.025 0.01 0.001
Crit value 1.64 2.71 3.84 5.02 6.64 10.83
 

Sig. 0.20: chi is greater than or equal to 1.64
Sig. 0.10: chi is greater than or equal to 2.71
Sig. 0.05: chi is greater than or equal to 3.84
Sig. 0.025: chi is greater than or equal to 5.02
Sig. 0.01: chi is greater than or equal to 6.64
Sig. 0.001: chi is greater than or equal to 10.83
Degrees of freedom: 1
Chi-square = 14.7806148884782
p is less than or equal to 0.001.
The distribution is significant.

---

Table D: Chi Square Comparison of Sex to PNE

 Male Female totals
Wet 13 21 34
Dry 30 104 134
totals 43 125 168
 

Table D Analysis

Degrees of freedom (df) = (rows - 1) x (columns - 1)
df = (2-1) x (2-1) = 1
Expected frequencies for each cell:
Row 1 column 1
Observed value (O) = 13
Expected value (E) = (row total x column total) / grand total
E = (34 x 43) / 168 = 8.70238095238095
Chi-square = (O - E)squared / E
Chi-square = ((13 - 8.70238095238095) **2) / 8.70238095238095
Chi-square = 2.12235359259983
Total chi-square now = 2.12235359259983
Row 1 column 2
Observed value (O) = 21
Expected value (E) = (row total x column total) / grand total
E = (34 x 125) / 168 = 25.297619047619
Chi-square = (O - E)squared / E
Chi-square = ((21 - 25.297619047619) **2) / 25.297619047619
Chi-square = 0.730089635854342
Total chi-square now = 2.85244322845417
Row 2 column 1
Observed value (O) = 30
Expected value (E) = (row total x column total) / grand total
E = (134 x 43) / 168 = 34.2976190476191
Chi-square = (O - E)squared / E
Chi-square = ((30 - 34.2976190476191) **2) / 34.2976190476191
Chi-square = 0.538507627973092
Total chi-square now = 3.39095085642726
Row 2 column 2
Observed value (O) = 104
Expected value (E) = (row total x column total) / grand total
 

Table D Analysis (cont.)

E = (134 x 125) / 168 = 99.7023809523809
Chi-square = (O - E)squared / E
Chi-square = ((104 - 99.7023809523809) **2) / 99.7023809523809
Chi-square = 0.185246624022744
Total chi-square now = 3.57619748045001
Probability (P):
Looking up critical values for chi at df = 1:

Sig levels 0.20 0.10 0.05 0.025 0.01 0.001
Crit value 1.64 2.71 3.84 5.02 6.64 10.83

Sig. 0.20: chi is greater than or equal to 1.64
Sig. 0.10: chi is greater than or equal to 2.71
Degrees of freedom: 1
Chi-square = 3.57619748045001
For significance at the .05 level, chi-square should be greater than or equal to 3.84.
p is less than or equal to 0.10.
The distribution is not significant.

---

 Table E: Chi Square Comparison of Sex to Handedness

         Male Female totals
Right     31 100 131
Left       12 25 37
totals     43 125 168
 

Table E Analysis

Degrees of freedom (df) = (rows - 1) x (columns - 1)
df = (2-1) x (2-1) = 1
Expected frequencies for each cell
Row 1 column 1
Observed value (O) = 31
Expected value (E) = (row total x column total) / grand total
E = (131 x 43) / 168 = 33.5297619047619
Chi-square = (O - E)squared / E
Chi-square = ((31 - 33.5297619047619) **2) / 33.5297619047619
Chi-square = 0.190866112111452
Total chi-square now = 0.190866112111452
Row 1 column 2
Observed value (O) = 100
Expected value (E) = (row total x column total) / grand total
E = (131 x 125) / 168 = 97.4702380952381
Chi-square = (O - E)squared / E
Chi-square = ((100 - 97.4702380952381) **2) / 97.4702380952381
Chi-square = 0.0656579425663392
Total chi-square now = 0.256524054677791
Row 2 column 1
Observed value (O) = 12
Expected value (E) = (row total x column total) / grand total
E = (37 x 43) / 168 = 9.47023809523809
Chi-square = (O - E)squared / E
Chi-square = ((12 - 9.47023809523809) **2) / 9.47023809523809
Chi-square = 0.675769207745952
Total chi-square now = 0.932293262423743
Row 2 column 2
Observed value (O) = 25
 Table E Analysis (cont.)

Expected value (E) = (row total x column total) / grand total
E = (37 x 125) / 168 = 27.5297619047619
Chi-square = (O - E)squared / E
Chi-square = ((25 - 27.5297619047619) **2) / 27.5297619047619
Chi-square = 0.232464607464608
Total chi-square now = 1.16475786988835
Probability (P):
Critical values for chi at df = 1:

Sig levels 0.20 0.10 0.05 0.025 0.01 0.001
Crit value 1.64 2.71 3.84 5.02 6.64 10.83
 

Degrees of freedom: 1
Chi-square = 1.16475786988835
For significance at the .05 level, chi-square should be greater than or equal to 3.84.
p is less than or equal to 1.
The distribution is not significant.