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:
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.
Enter: l = 1.4469
  r = 0
  CL = .85
Press Calculate
Solves for: t = 1312000