# Thread: how to show this

1. ## how to show this

$\displaystyle \phi_{n}=(1-\frac{x}{T_{n}})^{n-1} , \ \ T_{n}\geq x , \ \ \ 0 \ \ \ otherwise$

$\displaystyle X_{i} \ \ \ iid \ \ \ E(\lambda) , \ \ \ T_{n}=\sum_{1}^{n}{X_{i}}$

show that, $\displaystyle E(\phi_{k}|T_{n},\lambda)=\phi_{n} \ \ \ k\leq n$

2. you need to know the distribution of

$\displaystyle {X_1\over X_1+\cdots +X_n}$