Chapter II. Literature Review
3.2. Sampling procedures
In the main research, participants were sampled by using multi-stage sampling design. The details of sampling procedures are described into four parts, namely:
(3.2.1) determination of sample size, (3.2.2) multi-stage sampling procedure, (3.2.3) data collection procedure, and (3.2.4) number of participants and response rate of questionnaires.
3.2.1. Determination of the Sample Size
The present study employed structural equation modelling (SEM) to validate and test the invariance of the hypothesized structural models across cultural groups.
Therefore, the sample size was determined according to Hair et al. (1998), who suggested that an appropriate sample size for SEM analysis should be in a range of 5 to 10 participants for each parameter estimate. The present research model had approximately 50 parameter estimates (by considering only factor loadings and causal paths). Hence, an appropriate sample size would be in a range of 250 to 500 participants.1 However, the present study required two samples due to its cross-cultural research design. Therefore, each sample required at least 250 participants.
3.2.2. Multi-Stage Sampling Procedures
After an adequate sample size was determined, participants were recruited using multi-stage sampling based on the following three sampling units: region, school type, and grade level..
Region
The State of North-Rhine-Westphalia (NRW) in Germany, and the Bangkok Metropolitan Area and Chonburi Province in Thailand, were selected purposely.
1 In the current research, parents provided information about their motivational beliefs, interpersonal conditions, and family contexts. Pupils provided information about their perceptions on the quality of home-based parental involvement and academic functioning outcomes. The conceptual model empirically investigated the linkages between parent variables and pupil variables. Therefore, in one unit of analysis, one participant referred to one parent–child dyad.
School Type
In the present study, family SES was a crucial research variable. To recruit a variety of participants with different SES, school type was used as one of sampling units. The German school system begins with primary education (Grades 1 to 4), followed by lower secondary education (Sekundarstufe I; Grades 5 to 9 or 10) and upper secondary education (Sekundarstufe II; Grades 11 to 12 or 13). At the level of primary education, pupils are taught together. To pursue their secondary education (at 5th grade), they are sent to four different school tracks depending on their school performances and the recommendations of their primary school teachers. The four school types are Hauptschule, Realschule, Gymnasium, and Gesamtschule.
The Hauptschule is the lowest school track. This school type provides secondary education until the 9th or t10th grade (Hauptschulabschluss). The Realschule is the middle school track. This school type provides secondary education until 10th grade (Realschulabschluss). The Gymnasium is the highest school track. This school type provides secondary education until 13th grade.
After completing 13th grade, pupils receive the higher education entrance qualification (Abitur). The Gesamtschule combines all three school tracks mentioned above (see Rosebrock, 2006, for greater detail on the German school system). Generally, each track in the German school system takes pupils from different social backgrounds (Baumert & Schümer, 2001; Rekus et al., 1998, as cited in Rosebrock, 2006). Therefore, the present study recruited German participants from all four school types.
The Thai school system begins with primary education (Grades 1 to 6) followed by lower secondary education (Grades 7 to 9) and upper secondary education (Grades 10 to 12). The upper secondary school is divided into academic and vocational tracks. Unlike the German school system, Thai pupils are not split into different school tracks after 4th grade on the basis of their achievement.
Therefore, school types in Thailand were classified by the jurisdictions of the schools—in other words, the governmental institutions that administer, control, and promote them. Schools are under the control of four governmental institutions, namely, the Local Administration Organizations (LAO),2 the Office
2LAO = municipality school with a small number of pupils. The LAO schools are normally located in temples.
of the Basic Education Commission (OBEC),3 the Office of Higher Education Commission (OHEC),4 and the Office of the Private Education Commission (OPEC).5 Basically, schools under the administration of different governmental institutions vary in terms of the number of pupils, the number of teaching staff, the size of the administrative budget, and so forth. Therefore, it could be assumed that the four school types in Thailand represented pupils from different social backgrounds.
Grade Level
Cotton and Wikelund (1989) stated that parental involvement in their child’s education might have more powerful effects on children during the earlier educational process. Furthermore, previous studies have found that the levels of parental involvement decrease in higher grade levels as children grow older (e.g.
Eccles & Harold, 1996; Green et al., 2007; Grolnick & Slowiaczek, 1994). There may be several reasons for decreases in the levels of parental involvement. For instance, older pupils are more likely to take personal responsibility for their homework. Therefore, pupils may need less support from their parents or profit more from other kinds of homework assistance (Wild & Yotyodying, 2012).
As a result, the current research, therefore, focused on home-based parental involvement for pupils in earlier stages. It purposely recruited pupils from the 5th and the 6th grades because, in Germany, the pupils’ transition to the four school types first begins at 5th grade.
3.2.3. Data Collection Procedures
Data were collected from participants in Germany and Thailand. The details of data collection procedures are divided into two phases: (a) data collection in Germany and (b) data collection in Thailand.
Data Collection in Germany
Data collection started in Germany and proceeded from March to May 2010. One year before the data collection, participants were recruited by contacting schools
3OBEC = public school with a large number of pupils.
4OHEC = laboratory school or demonstration school of public universities with a large number of pupils. Most of the children of university staff attend this school type.
5 OPEC = private schools with a large number of pupils. A high tuition fee is normally required.
taking part in the PARS Study.6 The present study was officially presented to the principal or representative of each school at the first meeting of PARS on May 27, 2009. The meeting took place at the Institute for School Development Research (IFS), TU Dortmund University. The aim of the first PARS meeting was to inform school principals about the aims and working procedures of the longitudinal study being carried out by the International NRW-Research School “Education and Capabilities”. Apart from this, doctoral students receiving scholarships at the Research School, who needed schools to participate in their own dissertation projects, were invited to give small talks. School principals were informed that participation in each dissertation project is voluntary.
The plan was to recruit participants from eight schools (two schools for each school track). Only seven schools agreed (one Hauptschule, two Realschule, two Gymnasium, and two Gesamtschule). Because of the need to obtain pupils and parents from one more Hauptschule, the principal of the last Hauptschule was contacted directly. To inform school principals about the project in greater detail, an information sheet was sent to them by post afterwards. Moreover, the principal of each school was asked to distribute parental consent forms to parents via their children.
Overall, eight schools (16 classrooms; eight classrooms per 5th and 6th grade) were visited, and pupils were asked to complete the questionnaires. Every school gave permission to administer the questionnaires in pupils’ regular classrooms during pupils’ regular class periods. First of all, pupils were told about the different types of questions they would find inside the questionnaire (e.g. yes–
no question, rating scale) and told that all of their responses would remain confidential. After the pupils had completed both questionnaires, they were given the parent questionnaires with a stamped and addressed envelope. Pupils were asked to deliver these to their parents7 by hands when reaching home. They were told to give the parent questionnaire to the parent who was most often responsible for their homework and school activities. To retain confidentiality, parents could
6 The panel Study at the International NRW-Research School “Education and Capabilities” is a longitudinal study in the German federal state of North Rhine-Westphalia (NRW). The PARS study is being implemented by the Institute of School Development Research (IFS) as a source of empirical data for the Research School. The PARS study aims to investigate pupil academic development (secondary school) in relation to personality characteristics, families, and schools.
7 Parents refer to biological parents (father and mother), adoptive parents, step-parents, and primary caregivers (e.g. grandparents, relatives) with whom pupils live and who play the most important role in home-based parental involvement.
decide to send the completed parent questionnaires back to us either by post or via the classroom teachers. School principals and classroom teachers reminded their pupils about the need to return the completed questionnaires.
Data Collection in Thailand
After finishing the first data collection in Germany, the second data collection was carried out from July to August 2010 in Thailand. To request participation, official letters from the Research School were sent to the principals of the eight schools. All schools agreed to participate. Before starting the data collection, information sheets about the study and parental consent forms were distributed to parents.
Eight schools were visited in the Bangkok Metropolitan Area and Chonburi Province (16 classrooms, eight 5th-grade classes, eight 6th-grade classes). Pupils were asked to complete the questionnaires during regular class periods and in their regular classrooms. The test administration procedures were the same as those applied in Germany.
3.2.4. Number of Participants and Response Rates of the Parent and Pupil Questionnaires
Table 3.4 shows the number of participants and response rates of pupil and parent questionnaires by school type. For the data collection in Germany, 386 pupil questionnaires were distributed and all of them were returned at the end of testing (response rate = 100%). Of the 386 parent questionnaires distributed via pupils, 288 were returned (response rate = 75%). For the data collection in Thailand, 535 pupil questionnaires were distributed and returned at the end of each testing session (response rate = 100%). Of the 535 parent questionnaires distributed via pupils, 494 were returned (response rate = 92%). Overall, the response rate for the parent questionnaire in the Thai sample was higher than that in the German sample. In the German sample, the highest response rate for the parent questionnaire was from parents of Gymnasium pupils (83%) followed by parents of Gesamtschule pupils (77%) and parents of Realschule pupils (68%). In the Thai sample, the highest response rate for the parent questionnaire was in the parents of the OHEC pupils (100%) followed by parents of the OPEC pupils (94%), parents of the LAO pupils (89%), and parents of the OBEC pupils (88%). Therefore, to cope with the issue of missing data, only data from complete parent–child dyads
were analysed. This resulted in complete databases for 288 German parent–child dyads and 494 Thai parent–child dyads.
Table 3.4
Number of Participants and Response Rates on Pupil and Parent Questionnaires by School Type
School type
Pupil Parent
Number of questionnaires
distributed N
Number of questionnaires
returned N
Response rate
%
Number of questionnaires
distributed N
Number of questionnaires
returned N
Response rate
% Germany
Hauptschule 84 84 100.00 84 59 70.20
Realschule 107 107 100.00 107 73 68.20
Gymnasium 99 99 100.00 99 82 82.80
Gesamtschule 96 96 100.00 96 74 77.10
Total 386 386 100.00 386 288 74.60
Thailand
Local Admin 113 113 100.00 113 101 89.40
Basic education 241 241 100.00 241 218 87.90
Higher education 89 89 100.00 89 89 100.00
Private education 92 92 100.00 92 86 93.50
Total 535 535 100.00 535 494 92.30
A multiple group analysis was performed in order to test the measurement invariance of the empirical models across two samples. Ideally, the number of participants in each group should be equal. However, hardly any research has indicated whether unequal sample sizes impact on the findings when performing multiple group analysis (Division of Statistics and Scientific Computation, 2011).
In this study, the number of participants in each sample was sufficient for the parameter estimation (greater than 250 participants). Hence, unequal sample sizes should not be problematic.