how to sum up

[Vera]

Hi,

we try to sketch a probability that is dependand on the effecitivity of inspections and the number of inspections.
e = effectivity
n = number inspections

Formula:
∑ (from 0 to n) (1-e)^(n-1)*e
so, if effectivity is 0,4, the probabilbility is 0,4 if one inspection, and 0,64 with to inspections and so on...
how can I formulate an equation in vensim to achieve this?

Thanks,
Vera

[bob@vensim.com]

Hi Vera,

This is just a simple algebraic series

sum r^n from 0 to N is

1/r - r^(N-1)


with 0 < r < 1 - so just manipluate your expression.

Bob Eberlein

[Vera]

Thank you!