to Ortuno-Sierra, Fonseca-Pedrero, Paino, Riba and Muniz (2015), assessing
emotional and behavioural problems among adolescents and children is the main
issue in many fields such as clinical and public health policy. Besides that,
studies shown that particularly some percentage of children and adolescents
suffer from at least one psychiatric disorder mainly the youths with problems
such as anxiety, depression, oppositional-defiant disorder and attention-deficit
and hyperactivity disorder (ADHD) (Muris, Meesters & van den Berg, 2003).
Based on Mathai, Anderson and Bourne (2004), about 20% of children and
adolescents in Western countries suffer from mental diseases (as cited in Riso,
Salcuni, Chessa, Raudino, Lis & Altoe, 2010).

            Different types of psychopathologies can be
measured using questionnaires and it is important due to the fact that not many
children or adolescents realise the existence of psychiatric disorders. In that
case, the particular person failed to approach the mental health institutions
for help to solve the psychiatric problems. Thus, this questionnaire method can
help anyone to detect such behavioural and emotional problems at early stage
itself (Muris, Meesters & van den Berg, 2003). Otherwise, the psychiatric
problem will be at severe stage due to unawareness. However, assessment can be
done using self-report SDQ as well.

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and Difficulties Questionnaire (SDQ) contains 25 items which are divided among
five types of subscales. The subscales are emotional problems, hyperactivity,
conduct problems, peer relationships and prosocial behaviour (Goodman, 1997).
This questionnaire can be conducted as self, parent or teacher report. It is
being used in among many populations to assess the different types of
psychopathologies that occur among children and adolescents.

A study by
Moriwaki and Kamio (2014) was conducted on Japanese students sample aged 7 to
15 whom attending to primary or secondary schools. The study comprised of large
sample consist of 24519 parent ratings and 7977 teacher ratings. The result of
this study achieved strong internal reliability, satisfactory inter-rater
agreement, excellent test-retest reliability and satisfied convergent and
divergent validity.

Besides, a
study conducted by Goodman (2001) recruited 10438 British participants at the
age range of 5-15 years old. Parent-teacher report and self-report for
11-15year olds was used in this study. The result from this study shown
satisfactory internal consistency reliability (Cronbach ?=0.73) and retest
stability with mean of 0.62. This states that SDQ is a reliable measure of
psychopathology for children and adolescents. Another study revealed high
test-retest reliability in older children more than the younger children except
the internal reliability for peer problems was highly questionable for both
category (Mellor, 2004).

However, a
weak internal reliability was shown when the SDQ was conducted as self-test and
parent among Chinese adolescents while the inter-rater agreement shown moderate
result in both self and parent report (Mellor et al., 2016). Other than that,
Dutch parents and teachers were asked to report in behalf of the children aged
4 to 8. The data was analysed using both exploratory and confirmatory factor
analysis in which was found that the internal consistency and interrater
reliability was not good in conduct problems and peer problems (Leeuwen et al.,

Meanwhile, another
study by Goodman and Scott (1999) was conducted among with mothers of children
aged 4 to 7 whom were divided into two groups as low-risk and high-risk groups.
The study shown good convergent validity where the questionnaire was able to
differentiate high and low-risk children. In addition, Stone et al. (2010)
studied 48 studies on reliability and validity of the parent and teacher SDQ
and the subjects were children of 4 to 12 years old. The result shows
satisfactory reliability and the validity confirmed the five-factor structure
of SDQ through 15 out of 18 studies.

Whereas, a study by
Kersten et al. (2016) conducted experiment on children aged 3 to 5 years. This
study emphasized on different types of validity such as content, cultural,
convergent, structural and discriminant validity. The result shown lack of
support for discriminant validity even though other types of validities shown
satisfactory result. There was also lack of evidence for the cultural validity
and criterion validity.

                        This study involves the study of
psychometrics in reliability and validity of the Strengths and Difficulties
Questionnaire (SDQ). The main aim of this study is to measure the impact of
different types of reliability and validity of the Strength and Difficulties
Questionnaire among Nigerian population.