摘要：In this research for determining outlier data by traditional methods, has used [Mean ± 3S], Box plot, Grubbs' Test and Grubbs and Beck Test. Based on the traditional methods and the box plot (boxplot), discharge of 783 m/s was determined in 2004-2005 water year. as the outlier data in the data series of Annual maximum instantaneous peak streamflow in Tamer hydrometric station. The station is located in the outlet of Tamer watershed in Iran in an area about 1,531 square kilometers southern Caspian Sea coastline. Moreover, the outlier data in Grubbs Test was achieved in two modes observational data series and normalized data series. Based on this, discharge of 783 m/s in observational data series was determined as the outlier data. After normalizing the data using Box-Cox transformation, no outlier data were achieved using Grubbs Test. By using Grubbs-Beck relation, no outlier data were obtained in Tamer hydrometric station.
