Poisson Distributions

     
Failure Rate (l)  per 106 Hours
Time (t)  Hours
Max. No. of Failures (r)  
Confidence (CL)  
     
     

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 106 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