View Full Version : an easy one this time

09-16-2005, 08:54 AM
I have two questions that say to consult any standard probability text for the answer, but I can't find it there, and I just spent a half hour looking online for it.

I need the variance (I did the calculation but it says to look up the answer and supply it) for the following two equations:
- (1-p)^(k-1)*p
- L*e^(-Lx), L being lambda. also for this one, if someone can confirm the E(x) I'd appreciate it. I'm getting 1/L, but I ran the intergral on the integrator and it's giving me -1/L


09-17-2005, 01:14 PM
You cannot compute the variance of an equation, only of a random variable. Your second equation looks like a probability density function for x, defined on the interval 0 to infinity, but it would be nice if you specified this. Your first equation could be a density function for p on the interval 0 to 1, but it doesn't integrate to 1. Perhaps a constant is missing?

If you supply more information, the integrations are not difficult.