پديدآورندگان :
Homei H Department of Statistics, Faculty of Mathematical Sciences, University of Tabriz, Tabriz, Iran , Albad E Department of Statistics, Faculty of Mathematical Sciences, University of Tabriz, Tabriz, Iran , Fallahi M Department of Statistics, Faculty of Mathematical Sciences, University of Tabriz, Tabriz, Iran
چكيده فارسي :
The paper is motivated by considering lifetime in the environment. The distribution of the product of Gamma and Beta independent random variables have been studied by several authors such as Nadarajah and Kotz. (2005). On the product and ratio of gamma and beta random variables. Allgemeines Statistisches Archiv 89, 435--449]. Following [SM. Abourizk, DW. Halpin, JR. Wilson (1994). Fitting beta distributions based on sample data. Journal of Construction Engineering and Management, 288-305] we are taking the sum of beta random variables under environmental impact and then a suitable approximation is presented for the case that the distribution can not be evaluated. Finally the obtain result lead us to lifetime distribution in independent $r$-position.
