The present work evaluated the sample variability of the Gamma distribution parameters fitted to monthly precipitation series in the regions of Campinas-SP and Pelotas-RS, which have data for the 1890-2006 and 1890-2005 periods, respectively. So, the sample spaces considered were of 58, 39 and 29 years for Campinas, and of 58 and 29 years for Pelotas. Analyses were done using the likelihood ratio test. The analyses showed significant sample alterations. No trend was detected in monthly precipitation series of the region of Campinas-SP. Increasing trends was detected in the monthly precipitation series of the region of Pelotas-RS considering the 1948 to 1976 and 1977 to 2005 samples.
sample space; likelihood ratio test