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Chapter 3
indicates how many standard deviations a measurement is above or below the mean of the normal distribution.
Statistical analyses
Descriptive statistics (means ± SD) were used to describe the study sample with regard to demographic characteristics stratified by ethnic background (Table 1). Mean YSR and CBCL scores were compared with the reference group (norm data) by a one-sample test. Group comparisons between adolescents and parents (Table 2), on the eight syndrome scales, the Internalizing and Externalizing scale, and the Total Problem scale were tested with paired t-tests. Group comparisons between both ethnicities (western and non-western) (Table 3) were examined by linear regression analysis adjusted for age, sex and BMI. β-coefficients represent the mean difference between both ethnicities. Descriptive statistics was used to describe the study sample with regard to the percentage of the adolescents who had behaviour scores outside the normal range (e.g. in the borderline and clinical range; Figure 1). Data were analysed using SPSS 20.0. The significance level was set at p<0.05.
Results
Participants
Adolescents were recruited from May 2006 to June 2008. Of the 128 invited adolescents who provided informed consent, 109 (85%) return the questionnaires. There were no significant differences in baseline characteristics between participants and the 19 adolescents who did not fill in the questionnaires. Table 1 shows the characteristics of these 109 adolescents (56% girls) by ethnicity. There were no significant differences in these characteristics between western and non-western adolescents except for mean BMI and BMIsds, which were higher among the non-western adolescents (see Table 1).
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