NATIONAL

HEALTH BEHAVIOUR IN SCHOOL-AGED CHILDREN:
WHO COLLABORATIVE CROSS-NATIONAL STUDY (HBSC)
2014 SURVEY IN SCOTLAND NATIONAL REPORT
RESULTS
PRESENTATION OF FINDINGS
This chapter, the first of 15, gives a broad introduction and background to the study. Chapters 2 to 5 give a descriptive
summary of social factors which are known to be associated with the health behaviour of young people: family life, the
school environment, peer relations and neighbourhood environment. The following chapters focus on health and wellbeing
indicators and health and risk behaviours. They present prevalence by age and gender and over time, where data
are available. Most of the findings presented in this report are based on collapsing response options to questionnaire
items.
SAMPLE SIZE AND PRECISION OF ESTIMATES
The basic national sample size within each age group was set at around 2000 students (before addition of boost areas), to
allow more scope in subgroup analyses. The sample was selected using cluster sampling by school class, rather than simple
random sampling. If cluster sampling methods are not accounted for in analysis, this can result in underestimation of
standard errors, meaning that differences in prevalence may falsely be considered statistically significant. For example, for
a prevalence of 19%, the standard error under the assumption of random sampling is 0.8%. The true complex standard error
for this proportion, which takes account of the sample design (including clustering), is 1.2%, resulting in 95% confidence
intervals of 16.4%-21.0%. This compares with a falsely narrow confidence interval of 17.0%-20.3% under the assumption of
random sampling. All analyses in the report take account of sample design.
DATA ANALYSES
Design adjusted chi-square tests were carried out to assess statistical significance of differences between genders and age
groups. All differences or changes reported are statistically significant unless otherwise stated. In this report, a 99% level of
significance was used in the comparison of proportions. This more conservative measure was used in preference to 95%,
as many tests of proportions were carried out. Analyses for age and gender took account of the effect of the survey design
– stratification, clustering and weighting – on the precision of the estimates presented. The statistical package SPSS v21
(IBM) was used for all design-adjusted analyses.
Many of the items were collected over a number of surveys in Scotland and trends are reported for these. Where, for
example, differences ‘between 1990 and 2014’ are described, the statistical test carried out was between the proportion
in 1990 and the proportion in 2014. In some cases, comparisons were drawn between intervening years and these are
highlighted in the text.
INTRODUCTION AND METHODS
Where in some cases, reported data appear not to add up to 100%, this is due to rounding error.
NOTES:
i http://www.cahru.org
ii http://www.hbsc.org/
iii Perth and Kinross Local Authority
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