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:
A new product's failure rate was predicted to be 2.56 failures per million hours. The test plan was to acccumulate 2,500,000 hours of operational time. What is the maximum number of failures allowed to be 90% confident that the failure rate is 2.56? Using the calculator as indicated, with 3 or fewer failures in 2,500,000 hours, you would be 90% confident that the failure rate is 2.56 per million hours.
Enter: l = 2.56
  t = 2500000
  CL = .9
Press Calculate
Solves for: r = 3