| Statistics Toolbox | |
Inverse of the negative binomial cumulative distribution function (cdf).
Syntax
X = nbininv(Y,R,P)
Description
X = nbininv(Y,R,P)
R and P at the corresponding probabilities in P. Since the binomial distribution is discrete, nbininv returns the least integer X such that the negative binomial cdf evaluated at X equals or exceeds Y. Vector or matrix inputs for Y, R, and P must have the same size, which is also the size of X. A scalar input for Y, R, or P is expanded to a constant matrix with the same dimensions as the other inputs.
The negative binomial cdf models consecutive trials, each having a constant probability P of success. The parameter R is the number of successes required before stopping.
Example
How many times would you need to flip a fair coin to have a 99% probability of having observed 10 heads?
flips = nbininv(0.99,10,0.5) + 10
flips =
33
Note that you have to flip at least 10 times to get 10 heads. That is why the second term on the right side of the equals sign is a 10.
See Also
icdf, nbincdf, nbinpdf, nbinrnd, nbinstat
| | nbincdf | nbinpdf | |