## 3 Methodology  
To achieve the proposed research objectives, this research study was divided into three main stages: research design, data collection, and data analysis and discussion, as shown in Figure 1.  
A questionnaire method was introduced in this research to obtain valuable opinions on the local industry practices and current statutory control mechanism of the external stone cladding system at the two stages: production stage and installation stage. From the background knowledge and critical issues reviewed from the case studies, a questionnaire was devised and created. Furthermore, pilot interviews were conducted with two building professionals to refine and finalize the questionnaire before it was released. The questionnaire was structured into three sections: (1) adequateness of statutory control and monitoring mechanism of the external stone cladding system, (2) factors to ensure the quality in the production stage, and (3) factors to ensure the quality in the installation stage. In the survey, the respondents had to make a decent score on a scale from the lowest (+1) to the highest level (+5) against each variable using a five-point Likert scale. The questionnaire was distributed by emails to 358 building-related companies and practitioners in Hong Kong. The questionnaire survey replies were provided by 53 respondents, representing a response rate of 14.8%. The groups of respondents were found to be Contractors (17 responses, 32.1%), Civil/Geotechnical/Structural Engineers (14 responses, 26.4%), Architects (12 responses, 22.6%), and Building/Quantity Surveyors (10 responses, 18.9%). The majority of the respondents had more than 10 years of experience in the construction industry, where 11 to 15-year is 28.3%, 16 to 20-year is 18.9%, and over 20 years is 15.1%. Since the respondents may have varied perspectives depending on their workgroup, several statistical tests were further introduced to find out any significant differences in the level of importance rated by the workgroups. The data obtained from the respondents were grouped into two types,  
Figure 1: Research flow chart. responses from the design team and the construction team, based on their main perspectives for design or construction aspects of the external stone cladding system. The design team included civil/geotechnical/structural engineers, architects, and building surveyors, while the construction team consisted of contractors, subcontractors, and building engineers. Quantity surveyors, representing aspects of neither design nor construction solely, were not included in both groups. The approach and procedures used to conduct statistic tests for two independent groups were formulated and are shown in Figure 2.  
Shapiro-Wilk test is used in this study for a normality assessment of data. The normality assessment of data is a prerequisite for some statistic tests, as the normal distribution of a variable is an underlying criterion when the parametric test is used. 'Anderson-Darling' [14], 'Kolmogorov-Smirnov' [15], and 'Shapiro-Wilk' [16] are the normality test commonly adopted to determine the statistical data if a variable in a population is normally distributed. It is claimed that 'Shapiro-Wilk' test has higher statistical power than others for a given significance [17]. The null-hypothesis (H0) of the Shapiro-Wilk test is that the data tested is typically distributed in the population. If the value of \(p\) (sig.) is more significant than 0.05, the data is considered to be a normally distributed population in this research study. The test statistic is calculated as below. \[W\ =\ \frac{\left(\sum_{i=1}^{n}a_{i}x_{(i)}\right)^{2}}{\sum_{i=1}^{n} \left(x_{i}-\overline{x}\right)^{2}}, \tag{1}\]  
where  
\(x_{(i)}\) = sample mean, and  
\(\overline{x}=i^{th}\) order statistic. The Mann-Whitney \(U\) test, also known as the Wilcoxon rank-sum test, was conducted in this study for a non-parametric variable to compare if there was a statistical difference between two independent.