Statistics Toolbox™

poisscdf - Poisson cumulative distribution function

Syntax

P = poisscdf(X,lambda)

Description

P = poisscdf(X,lambda) computes the Poisson cdf at each of the values in X using the corresponding parameters in lambda. X and lambda can be vectors, matrices, or multidimensional arrays that have the same size. A scalar input is expanded to a constant array with the same dimensions as the other input. The parameters in lambda must be positive.

The Poisson cdf is

Examples

For example, consider a Quality Assurance department that performs random tests of individual hard disks. Their policy is to shut down the manufacturing process if an inspector finds more than four bad sectors on a disk. What is the probability of shutting down the process if the mean number of bad sectors (λ) is two?

probability = 1-poisscdf(4,2)
probability =
  0.0527

About 5% of the time, a normally functioning manufacturing process produces more than four flaws on a hard disk.

Suppose the average number of flaws (λ) increases to four. What is the probability of finding fewer than five flaws on a hard drive?

probability = poisscdf(4,4)
probability =
  0.6288

This means that this faulty manufacturing process continues to operate after this first inspection almost 63% of the time.

See Also

cdf, poisspdf, poissinv, poisstat, poissfit, poissrnd

plsregress

poissfit