3.1 IntroductionThis research will be conducted to study the influence leadership attribute of principals in the implementation of school-based assessment (SBA). This section contains the research design, population, sampling technique, and sample size. Additionally, a discussion on the unit of analysis, data collection procedures, instrument, validity of the instrument, data analysis plan, validity and reliability of the research are also included .3.2 Research DesignThis research will use a mixed method, a combination of qualitative and quantitative. Rossman and Wilson (1985, cited by Johnson, Onwuegbuzie, & Turner, 2007) identified three reasons for combining qualitative and quantitative research. First, combinations are used to enable or expand the analysis to provide richer data. Second, combinations are used to enable mutual confirmation or validation through triangulation. Finally, combinations are used to initiate new types of thinking by attending to paradoxes that emerge from both data sources. The mixed method uses previous research and/or more than one type of survey perspective.3.3 PopulationAccording to Doone (2008), the term "population" is used to represent all possible outcomes of interest to us in a particular study. Populations can be defined by locality or by social, biological or cultural criteria. The population of this research will be the school principal and all teachers of SMK Convent Klang. This study is a census where the population is equal to the number of respondents. Using the census as a research method provides a true measure of the population (without sampling error), baseline data can be obtained for future studies as well as detailed information on small...... middle paper..... .insured. The goal is to check for errors and ambiguities and the instruments that will be used must be validated (Salkind, 2006). The instrument in this study was validated by an associate professor of one of the IPTAs in Malaysia. She holds a PhD in Instructional Technology from the International Islamic University Malaysia (2007) with areas of expertise in Instructional Design and Technology, E-Learning, Design and Development Research.3.10 Reliability of Research Joppe (2000) defines reliability as the extent to which results are consistent. over time. He also stated that an accurate representation of the total population studied is called reliability and if the results of a study can be reproduced using a similar methodology, then the research instrument is considered reliable (p. 1). Research reliability can be tested using Cronbach Alpha.