| [ QuizWit ] in KIDS 글 쓴 이(By): pinkrose (mirantz) 날 짜 (Date): 1998년 11월 27일 금요일 오전 08시 35분 45초 제 목(Title): [a2] poisson distribution Oh dear E.T.(?) you got me! when i first saw your posting about the impossibility of negative poisson parameter, i was kinda suprised and a little bit upset because of my neglence in detail. ^^ so i gave a thought for a minute and it was not that hard to patch the hole. if X is poisson with /ramda then -(-X) is poisson with /ramda hence if ramda_1 - ramda_2 < 0 then X2 - X1 is poisson with ramda_2 - ramda_1 this means X1-X2 may not be poisson but X2-X1 will be. so if f(X) is the density of -X then f(-X) will be the density of X. i hope my argument using the symmetry is very clear. ^^ hmm... by the way this is kinda neat. when i teach probability course, i will give this as a homework to students. |