# Math Help - Expectation

1. ## Expectation

The time interval Y between successive feedings of a certain type of insect has an exponential distribution with mean proportional to a positive measured characteristic x of the insect. Suppose we observe n independent insects, observing time intervals Y1, . . . , Yn with associated characteristics x1, . . . , xn.

Let E(Y)=a.

I have need to calculate $E(Y{_1}/X{_1})$. I supposed they were independent and then using the information i have E(Y)=cX so I get a/(c/a)=a^2/c. I think however that it is wrong.

2. ## Re: Expectation

It doesnt sound like Y and X are indep at all
Furthermore that would be E(YlX) not E(Y).