## 2 Materials and Methods
### Data Collections  
The data collected from the interviews with the owners or the senior executives with many units or many projects for the housing development located in large cities are from Bangkok, Nonthaburi, Samut Prakan, and Pathum Thani. The data that are difficult to access; therefore, it takes quite a long time to request a meeting for direct interviewing, and  
Figure 1: Research procedure.  
we obtained the data with a total of 1649 units divided into 15 types from many projects in Bangkok and the perimeter in Thailand, as shown in Table 1.  
To specify the number of house units as a sample size, the reference information of the population was collected from Real Estate Information Center, REIC [13]. The statistical data are shown in Figure 2.  
According to Figure 2, the average number of new houses for sale between 2017 and 2020 was 45,804 units. In order to determine the sample size, we used [PERSON]'s formular [14], which is presented in Equation (1).  
\[n=\frac{N}{1+N\left(e\right)^{2}} \tag{1}\]  
where \(n\) = sample size required, \(N\) = number of people in the population, and \(E\) = allowable error %.  
It reveals that the acceptable sample size was 397 units. However, the data collected for this study were 1649 units from many projects that are located in Bangkok, and perimeter areas are shown in Table 1.  
Table 1 shows the data of the housing development project located in Bangkok and perimeters (Nonthaburi, Samut Prakan, and Pathum Thani) that were obtained from an interview with the owner of 1649 units from 15 types. Then, we used the data of variables  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **House** \\ **Types** \\ \end{tabular} } & \multirow{2}{*}{**Units**} & \multirow{2}{*}{\begin{tabular}{c} **Land** \\ **Cost/Type** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **House** \\ **Building** \\ **Cost/Type** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Cultity** \\ **Cost** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Construction** \\ **Management Cost** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Marketing** \\ **Cost** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Land** \\ **Area** \\ **(Type)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Usable** \\ **Area** \\ **(Type)** \\ \end{tabular} } \\
1 & 197 & 675,107 & 1,335,600 & 330,817.76 & 49,706.26 & 75,858.09 & 50.7 & 106 \\
2 & 123 & 704,402.0 & 1,508,000.0 & 330,817.76 & 60,960.90 & 79,149.77 & 52.9 & 130 \\
3 & 107 & 752,338.0 & 1,985,600.0 & 330,817.76 & 68,463.78 & 84,536.14 & 56.5 & 146 \\
4 & 66 & 438,314.5 & 845,152.0 & 189,315.9 & 54,080.00 & 55,717.70 & 16 & 88 \\
5 & 271 & 520,498.4 & 1,252,184.0 & 189,315.9 & 81,119.28 & 83,575.80 & 19 & 132 \\
6 & 65 & 630,077.0 & 1,583,824.0 & 189,315.9 & 103,242.72 & 106,369.20 & 23 & 168 \\
7 & 188 & 459,350.0 & 1,231,400.9 & 196,042.2 & 41,224.81 & 53,286.10 & 20.7 & 110 \\
8 & 138 & 527,697.7 & 1,379,120.3 & 196,042.2 & 45,647.10 & 61,214.66 & 23.78 & 121.8 \\
9 & 58 & 459,350.0 & 1,281,694.2 & 196,042.2 & 42,843.82 & 53,286.10 & 20.7 & 114.32 \\
10 & 41 & 527,697.7 & 1,428,530.79 & 196,042.2 & 46,913.83 & 61,214.66 & 23.78 & 125.18 \\
11 & 20 & 1,560,674.89 & 1,780,000.0 & 301,503.76 & 59,579.82 & 120,051.91 & 37 & 130 \\
12 & 18 & 1,518,494.48 & 1,525,000.0 & 301,503.76 & 52,705.22 & 116,807.27 & 36 & 115 \\
13 & 95 & 759,247.24 & 1,420,000.0 & 301,503.76 & 56,371.67 & 58,403.63 & 18 & 123 \\
14 & 70 & 553,055.24 & 880,000.0 & 112,786.26 & 11,034.39 & 172,626.83 & 19 & 87 \\
15 & 192 & 486,803.83 & 750,000.0 & 112,786.26 & 9385.57 & 33,533.26 & 16.9 & 74 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Summary statistics of the housing development project situated in Bangkok and the perimeter.  
Figure 2: Statistic of new houses for sale in Bangkok and perimeter of Thailand/years (units).  
used in the study of each house type from Table 1 by using these data for multiple regression analysis models in the next step.