help on probabilty - binomial

[salvomic]

(11-20-2017 09:46 PM)primer Wrote:  Dears,
I have an urgent request,
my daughter uses hpprime, student are studying probability at the moment, I'm really not an expert on that point myself, unfortunately.

She could find how to compute P(x=k) by using built-inbinomial(n,p,k)
But we could not find how to compute P(x<k) ?
anyone knows ?

I can't belive there is such option in hp prime.
cheap casio calc, offers function "Bcd" for that, what's the hp equivalent ?

Thank you.

I think you should use BINOMIAL_CDF(n, p,k,[k2]) that "returns the probability of k or fewer successes out of n trials..." optional k2 returns the probability for the two k-values, that is the probability of between k and k2...

Salvo

EDIT: most distribution in the Prime and CAS distinguish between Density and Cumulative values (and also Inverse).

i.e.: 100 trials, prob. ½ (50%) k=50
BINOMIAL(100,1/2,50) = 7.958E-2 (only upon 50)
BINOMIAL_CDF(100,1/2,50) = 0.539794 (cumulative, from 0 to 50)
BINOMIAL_CDF(100,1/2,50)-BINOMIAL(100,1/2,50) = 0.4602053... that the probability to have 49 successes on 100 trials, or BINOMIAL_CDF(100,1/2,49)
If I well understand your needs...