1001.0807 arXiv:1001.0807v2 [astro-ph.CO] 16 Apr 2010 Probing the cosmic acceleration from combinations of different data sets Yungui Gong, 1, ∗ Bin Wang, 1, 2, † and Rong-Gen Cai 1, 3, ‡ $^{1}$College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065, China $^{2}$Department of Physics, Fudan University, Shanghai 200433, China $^{3}$Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China Abstract We examine in some detail the influence of the systematics in different data sets including type Ia supernova sample, baryon acoustic oscillation data and the cosmic microwave background information on the fitting results of the Chevallier-Polarski-Linder parametrization. We find that the systematics in the data sets does influence the fitting results and leads to different evolutional behavior of dark energy. To check the versatility of Chevallier-Polarski-Linder parametrization, we also perform the analysis on the Wetterich parametrization of dark energy. The results show that both the parametrization of dark energy and the systematics in data sets influence the evolutional behavior of dark energy. PACS numbers: 95.36.+x, 98.80.Es $^{∗}$Electronic address: gongyg@cqupt.edu.cn $^{†}$Electronic address: wangb@fudan.edu.cn $^{‡}$Electronic address: cairg@itp.ac.cn 1