Chapter 2: Methodology
3.3 Phase Three: Comparison of sex differences between Vietnamese and Australian older
Phase three of the study examined possible sex differences in the total sample (of older adult
Vietnamese and Australians) on their sleep attitudes and beliefs as well as their level of
insomnia. Due to the non-normality of the data (which were presented previously), a
MANOVA could not be conducted and therefore, Mann-Whitney U tests were conducted for
the ISI, DBAS16 and SBS. The use of non-parametric tests such as the Mann-Whitney U
Test, was deemed unsuitable for analysis of the Sleep Plot because conceptually it is
important to consider the group of dependent variables together for the Sleep Plot. Therefore,
Fisher’s Exact Tests and Chi Square Tests were used to compare males and females on the Sleep Plots. The aim is first to compare if there are any differences between males and
females according to their scores on the Insomnia Severity Index (null hypothesis 3a).
3.3.1 Data screening for Insomnia Severity Index (ISI)
Prior to analysis, data screening revealed that the individual ISI scores were skewed and not
normally distributed (results were previously presented above) therefore, a series of Mann-
Whitney U tests were performed which are presented below.
3.3.2 Total males versus total females on ISI
The results indicated that there were no significant differences between males and females on
ISI total scores. Please refer to Table 3.33 for the descriptive statistics and summary of
Table 3.33
Descriptive statistics and summary of analyses of the Mann-Whitney for each ISI item as a function of sex for both the Australian and Vietnamese samples (entire sample) (* indicates significant difference between insomnia status groups at p < 0.05).
ISI Items Male
Mean (SD)
Female Mean (SD)
U Z P
1.* Difficulty falling asleep 1.31 (1.22) 1.81 (1.19) 3931.00 -2.99 0.01
2. Difficulty staying asleep 1.73 (1.11) 1.92 (1.16) 4683.50 -1.16 0.24
3. Problems waking up too early 1.69 (1.13) 1.80 (1.19) 4929.00 -0.56 0.57
4. How satisfied/dissatisfied are you with your current sleep pattern?
1.95 (1.07) 2.17 (1.12) 4628.50 -1.30 0.19
5. How noticeable to others do you think your sleep problem is in terms of impairing the quality of your life?
1.56 (1.26) 1.48 (1.30) 4951.50 -0.51 0.61
6. How worried/distressed are you about your current sleep problem? 1.51 (1.28) 1.70 (1.36) 4754.00 -0.99 0.32 7. To what extent do you consider your sleep problem
to interfere with your daily functioning (e.g. daytime fatigue, mood, ability to function at work/daily chores, concentration, memory, mood, etc.) currently?
1.71 (1.26) 1.75 (1.35) 5101.00 -0.14
-1.09
0.89
0.27
Total Scores 11.49 (7.17) 12.67 (7.41) 4698.00
3.3.3 Data screening for DBAS16
Prior to analysis data screening revealed that the individual DBAS16 scores (which varied
from 1-10) were not normally distributed (details above in phase 2) and therefore a Mann-
Whitney U test was performed comparing males and females across the whole sample
(Australian and Vietnamese).
3.3.4 Total males versus total females on DBAS16
The results indicated that there were no significant differences between males and females on
DBAS16 total scores. Given this, the significant result for item 4 is not considered to be of
importance. Please refer to Table 3.34 for the descriptive statistics and summary of analyses
Table 3.34
Descriptive statistics and summary of analyses of the Mann-Whitney for each DBAS 16 item as a function of sex for both the Australian and Vietnamese samples (entire sample)(* indicates significant difference between insomnia status groups at p < 0.05).
DBAS 16 Items Male
Mean (SD)
Female Mean (SD)
U Z P
1. I need 8 hours of sleep to feel refreshed and function well during the day. 7.25 (2.60) 7.55 (2.43) 4887.00 -0.75 0.45
2. When I don’t get proper amount of sleep on a given night, I need to catch up on the next day by napping or on the next night by sleeping longer.
6.37 (3.16) 6.86 (3.04) 4742.00 -1.09 0.27
3. I am concerned that chronic insomnia may have serious consequences on my physical health. 7.08 (3.19) 7.44 (3.13) 4681.00 -1.12 0.25
4. * I am worried that I may lose control over my abilities to sleep. 4.79 (3.64) 6.04 (3.50) 4223.00 -2.32 0.02
5. After a poor night’s sleep, I know it will interfere with my activities the next day. 6.86 (2.95) 7.23 (2.85) 4820.00 -0.91 0.36 6. In order to be alert and function well during the day, I believe I would be better off taking a
sleeping pill rather than having a poor night’s sleep.
4.43 (3.67) 4.63 (3.64) 5059.00 -0.34 0.73
7. When I feel irritable, depressed, or anxious during the day, it is mostly because I did not sleep well the night before.
5.94 (3.28) 5.77 (3.38) 5052.00 -0.35 0.72
8. When I sleep poorly one night, I know it will disturb my sleep schedule for the whole week. 3.96 (3.18) 4.72 (3.52) 4594.00 -1.44 0.14
9. Without an adequate night’s sleep, I can hardly function the next day. 5.12 (3.19) 5.88 (3.14) 4487.00 -1.69 0.09
10. I can’t ever predict whether I’ll have a good or poor night’s sleep. 5.65 (3.25) 7.11 (3.05) 4895.00 -0.73 0.46
11. I have little ability to manage the negative consequences of disturbed sleep. 6.69 (3.15) 6.03 (3.14) 4841.00 -0.85 0.39 12. When I feel tired, have no energy, or just seem not to function well during the day, it is
generally because I did not sleep well the night before.
6.22 (3.09) 6.52 (2.91) 4891.00 -0.60 0.55
13. I believe insomnia is essentially the result of a chemical imbalance. 5.29 (2.87) 5.30 (3.18) 5118.00 -0.05 0.95
14. I feel insomnia is ruining my ability to enjoy life and prevents me from doing what I want. 5.07 (3.51) 5.68 (3.47) 4672.00 -1.12 0.26
15. Medication is probably the only solution to sleeplessness. 4.28 (3.31) 4.53 (3.57) 4949.50 -0.46 0.64
16. I avoid or cancel obligations (social, family) after a poor night’s sleep. 4.91 (2.48) 5.38 (2.62) 46.24.00 -1.23 0.22
Total Scores 89.88 (37.30) 96.76 (37.49) 4503.00 -1.38 0.16
Post hoc analyses were also conducted, for completeness, examining possible sex differences
on the DBAS 16 within each ethnic group and no significant differences were found (see
Appendix H for further details).
3.3.5 Data screening for Sleep Beliefs Scale (SBS)
Prior to analysis data screening revealed that the individual SBS scores (which ranged from -
1, 0 and 1) ranged in skewness and distribution. As before, the non-normality of the SBS data
required a series of Mann-Whitney U tests.
3.3.6 Total males versus total females on SBS
The results indicated that there were no significant differences between males and females
according to the SBS for the entire sample. Please refer to Table 3.35 for the descriptive
Table 3.35
Descriptive statistics and summary of significance findings of the Mann-Whitney for each SBS item as a function of sex with the Australian and Vietnamese samples (entire sample).
SBS Items Male
Mean (SD)
Female Mean (SD)
U Z P
1. Drinking alcohol in the evening 0.08 (0.85) 0.04 (0.760 4874.50 -0.42 0.67
2. Drinking coffee or other substances with caffeine after dinner 0.01 (0.87) 0.09 (0.86) 4805.00 -0.70 0.47
3. Doing intense physical exercise before going to bed 0.05 (0.79) 0.13 (0.82) 4688.50 -0.69 0.48
4. Taking a long nap during the day -0.02 (0.89) 0.05 (0.88) 4808.00 -0.59 0.55
5. Going to bed and waking up always at the same hour 23.22 (151.45) 8.14 (90.83) 4790.00 -1.03 0.30
6. Thinking about one’s engagements for the next day before falling asleep -0.02 (0.79) 0.16 (0.85) 4385.00 -1.67 0.09
7. Using sleep medication regularly -0.02 (0.83) 0.09 (0.85) 4546.50 -0.97 0.33
8. Smoking before falling asleep -0.01 (0.74) 0.01 (0.80) 4837.00 -0.26 0.79
9. Diverting one’s attention and relaxing before bedtime 23.27 (151.44) 16.43 (127.91) 4784.50 -1.04 0.29
10.Going to bed 2 hours later than the habitual hour -0.17 (0.66) 0.77 (9.03) 4560.00 -1.35 0.17
11.Going to bed with an empty stomach -0.01 (0.78) -0.14 (0.81) 4582.50 -1.17 0.24
12.Using the bed for eating, calling on the phone, studying and other non-sleeping activities -0.03 (0.87) -0.04 (0.84) 5025.00 -0.38 0.96
13.Trying to fall asleep without feeling tired -0.07 (0.77) 0.79 (9.04) 4893.00 -0.48 0.63
14.Studying or working intensely until late at night 0.25 (1.37) 0.82 (9.04) 4680.00 -1.02 0.31
15.Getting up when it is difficult to fall asleep 23.18 (151.45) 8.31 (90.81) 4919.00 -0.71 0.47
16.Going to bed 2 hours earlier than the habitual hour -0.11 (0.74) 0.09 (0.75) 4322.00 -1.85 0.06
17.Going to bed immediately after eating -0.07 (0.81) -0.02 (0.84) 4900.50 -0.36 0.72
18.Being worried about the impossibility of getting enough sleep 0.05 (0.87) 0.05 (0.89) 5003.00 -0.09 0.92
19.Sleeping in a quiet and dark room 23.17 (151.45) 16.48 (127.90) 5132.50 -0.17 0.89
20. Recovering lost sleep by sleeping for a long time -0.02 (0.84) 0.04 (0.79) 4864.50 -0.55 0.58
Total Scores -0.24 (8.62) 0.31 (9.43) 4582.50 -0.44 0.66
Again for completeness, post hoc analyses were conducted, examining possible sex
differences on the SBS within each ethnic group and no significant differences were found
(see Appendix I for further details).
3.3.7 Data screening for the Sleep Plots
As previously reported in the analyses of the Sleep Plots above, the data was not normally
distributed but skewed. Therefore, a MANOVA could not be performed, but rather Chi
Square and Fisher Exact Tests were conducted.
3.3.8 Perception of sleep for a healthy 60 year old according to sex for Australian and Vietnamese samples (entire sample) on the Sleep Plots
A Fisher’s Exact Test (2X3) was conducted which revealed no significant difference were found between the frequencies reported across males and females with respect to the three
different plot shape categories (p = 0.58; Fisher’s Exact Test) for the sleep of a healthy 60
year old. The results also revealed that neither the male or female groups had many participants that chose the ‘correct’ answer (Non U Wake Shape), with only two male participants and one female participant drawing this shape out of a total of 161 participants.
The descriptive data clearly shows that most people thought that it was the U Shape that was
representative of a typical night’s sleep for a healthy 60 year old with 83% representing this. Please refer to Table 3.36 which shows the frequencies for the three different categories
Table 3.36
Frequencies of different categories of sleep plots between males and females about perception of sleep for a healthy 60 year old for the entire sample
U Shape Non U No Wake Non U Wake Total
Male Count 53 11 2 66
Expected Count 54.9 9.8 1.2
Female Count 81 13 1 95
Expected Count 79.1 14.2 1.8
Total Count 134 24 3 161
3.3.9 Perception of one’s own sleep according to sex for Australian and Vietnamese samples (entire sample) on the Sleep Plots
Investigation into the participants reporting of their own sleep was also conducted using the
Chi Square Test (2X3) which revealed no significant differences were observed between
males and females according to their own perceived Sleep Plots (X² = 2.53, df = 2, p = 0.28).
The descriptive data continue to show that most people thought that it was the U Shape that
was representative of a typical night’s sleep for themselves with 59.8% representing this.
Please refer to Table 3.37 which shows the frequencies for the three different categories
Table 3.37
Frequencies of different categories of sleep plots between males and females about perception of one’s own sleep for the entire sample
U Shape Non U No Wake Non U Wake Total
Male Count 38 17 13 68
Expected Count 40.7 13.0 14.3
Female Count 62 15 22 99
Expected Count 59.3 19 20.7
Total Count 100 32 35 167
Post hoc analyses were again conducted, for completeness, comparing males and females
within each ethnic group and are reported in Appendix J. No significant sex differences were
found within the Vietnamese and Australian samples for both the perception of sleep for a
3.3.10 Summary of significant findings for Phase 3
Sex differences according to the Insomnia Severity Index
Males and females did not differ on their ISI scores for the entire sample (null hypothesis 3a is accepted).
Sex differences according to sleep attitudes and beliefs
There were no significant differences between males and females according to the DBAS16 for the entire sample (null hypothesis 3b accepted for DBAS 16). (Post hoc
analyses, shown in Appendix H showed that there were also no significant differences
within each of the Australian and the Vietnamese samples).
There were also no significant differences between males and females according to the SBS for the entire sample (null hypothesis 3b accepted for SBS). Again post hoc
analyses also showed no significant differences between sex for each of the different
ethnic groups (Australian and Vietnamese) as shown in Appendix I.
In relation the perception of sleep for a healthy 60 year old, no significant difference was found between the frequencies reported across males and females with respect to
the three different plot shape categories for the entire sample (null hypothesis 3b
accepted for Sleep Plot for a healthy 60 year old).
No significant differences were found for males and females regarding the perception of their own sleep across the three different sleep plot categories for the whole sample
Appendix J shows post hoc analyses for the different ethnic groups as a function of sex and no significant differences were found for the perception of sleep for a healthy
60 year old as well as their own sleep between males and females.
The results also revealed that neither the male or female groups had many participants that chose the ‘correct’ answer (Non U Wake Shape). The descriptive data clearly showed that most people thought that it was the U Shape that was representative of a typical night’s sleep for a healthy 60 year old and also for their own sleep.