0
$\begingroup$

Is it possible that the sum of probabilities of geometric distribution for "$k = 1,...,n$", where k is number of trials until the first success, is not equal to 1?

I'm asking this, because I encounter a problem, when writing a program in a language, like Matlab, it's Scilab, and I observe that for probability $p = 0.6$, and $n = 10$ I do not get the sum of probabilities equal to $1$ (but very close to 1). Also, I noticed that the first value for cumulative distribution function is $0.6$, while using Matlab function cdfgeo, the first value is $0.84$, which gives the right result. So, is it possible that the sum of probabilities be not $1$?

As additional information, I use the formula: $$P_{X}(x) = (1-p)^{k-1}p$$ where $X$ is a geometric random variable, $p = \text{probability}$, and $k = \text{number of trials}$.

$\endgroup$
0

1 Answer 1

Reset to default
1
$\begingroup$

Note that $k$ can take on any positive integer value; it is not limited just up to $10$.

$\endgroup$
3
  • $\begingroup$ Yes, I understand, so it's normal that for n = 10 I get something like this ? $\endgroup$
    – wonderingdev
    Commented May 4, 2015 at 20:21
  • $\begingroup$ Yes. If you go up to $10$ and then stop, your probabilities would add up to somewhat less than $1$. $\endgroup$
    – paw88789
    Commented May 4, 2015 at 20:22
  • $\begingroup$ So, then it's really so, thank you. $\endgroup$
    – wonderingdev
    Commented May 4, 2015 at 20:23

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .