[SciPy-User] Mean arrivals per time unit -> Time between consecutive arrivals

Ram Rachum cool-rr@cool-rr....
Fri Nov 27 00:49:33 CST 2009


 <josef.pktd <at> gmail.com> writes:
> > YOu should take the interarrival time between two consecutive arrivals
> > to be exponentially distributed with rate lambda, where lambda is the
> > arrival rate. LIke this the number of arrivals in a fixed period is
> > Poisson distributed. I never tried, but I suppose scipy contains a
> > module to generate exponentially distributed rv's.
> 
> The sum of iid exponential distributed rvs is gamma distributed
> http://en.wikipedia.org/wiki/Gamma_distribution
> 
> all available in scipy.stats
> 
> Josef

I don't understand. So you mean that the exponential thing would NOT be the
right thing for the time between consecutive arrivals?

Also, why doesn't scipy automatically gives me the time between consecutive 
arrivals when I give the mean number of arrivals per time period?

Ram.



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