Poisson Distributions

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: 
Assume that your product has accumulated 2,500,000 hours of operation with 3 failures. The goal is to be 95% confident in establishing the product's failure rate. How many failures should one expect in one million hours? Using the calculator as indicated, you would be 95% confident that the population of product would have an average failure rate of 3.3 per million hours. 
Enter:  t  =  2500000 
 r  =  3 
 CL  =  .95 
Press Calculate 
Solves for:  l  =  3.3 

