This calculator calculates the Poisson Distribution for Confidence level, Failure Rate, Time or Maximum Number of Failures allowed to satisfy a set of given conditions. The formula is as follows:

where:

l

=

failure rate per 10^{6} operating hours

r

=

number of failures

t

=

time, expressed in hours

P(r)

=

probability of getting exactly r failures in time t

CL

=

confidence level

Example use of the Calculator:

The established failure rate is 1.4469 failures per million hours. Assume that no failures will be allowed. What period of time must be accumulated before you are 85% confident that the failure rate is 1.4469? Using the calculator as indicated, after 1,312,000 hours of operation without a failure, you would be 85% confident that the failure rate is 1.4469.