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A modified Box and Cox power transformation to determinethe standardized precipitation index |
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| รหัสดีโอไอ | |
| Creator | 1. Tanachot Chaito 2. Manad Khamkong |
| Title | A modified Box and Cox power transformation to determinethe standardized precipitation index |
| Publisher | Research and Development Office, Prince of Songkla University |
| Publication Year | 2561 |
| Journal Title | Songklanakarin Journal of Science and Technology |
| Journal Vol. | 40 |
| Journal No. | 4 |
| Page no. | 867 |
| Keyword | drought, non-normal, positivelyskewed distribution, rainfall, skewness |
| URL Website | http://rdo.psu.ac.th/sjstweb/index.php |
| ISSN | 0125-3395 |
| Abstract | The objective of this research was to create a new transformation method, based on a modification of the Box and Coxpower transformation (SMBC) by adding the ratio of skewness to two sample sizes, to characterized rought conditions with astandardized precipitation index (SPI). Along with the various classical data transformations, namely the Box and Cox powertransformation (BC), the exponential transformation, the Yeo and Johnson transformation, and a modification to BC by addingrange, the results of a simulation study showed that the BC and SMBC methods had similar efficiencies when transforminggamma data, Weibull data, and Pearson type III data to a normal distribution, and notably, SMBC performed particularly wellwith the latter. Drought conditions were evaluated using the SMBC transformation on real-life data from rain gauging stations atMuang (Lamphun), Mae Prik (Lampang) and Chom Thong (Chiang Mai), Thailand. The SMBC proved to be particularly usefulin determining the SPI. |
