-1

I need to set parameters in an exponential distribution. I know that every 5 seconds I can produce 4 object in average. What is the lambda value of exponential distribution?

marc_s
  • 732,580
  • 175
  • 1,330
  • 1,459
user3697187
  • 7
  • 2
  • 1
    This question appears to be off-topic because it is about stats (try http://stats.stackexchange.com). – Oliver Charlesworth Jun 29 '14 at 18:29
  • @OliCharlesworth This is not about stats. It's about knowing what the correct input to a stats-oriented program should be. – pjs Jun 29 '14 at 18:52
  • Perhaps; but it's still not a programming question. In general, off-topic questions should be close-voted as such, so the OP can get more directed help in the correct place. – Oliver Charlesworth Jun 29 '14 at 19:11
  • @OliCharlesworth Why do you think determining correct inputs is not a programming question? – pjs Jun 29 '14 at 19:58
  • Because it has nothing to do with programming (in its current form), and everything to do with maths! – Oliver Charlesworth Jun 29 '14 at 20:03
  • Excluding inputs and proper function parameterization seems to me a very narrow view of programming. – pjs Jun 29 '14 at 20:21

1 Answers1

1

Lambda is a rate, and rates are always quantity per time unit. Your lambda is 4/5 = 0.8 per second. Scale accordingly if your model is in milliseconds, minutes, hours, days, etc.

Potential pitfalls - The exponential distribution can also be parameterized by its mean, which is the inverse of the rate. If the long-run average is 4 per 5 seconds, the mean amount of time between objects is 5/4 = 1.25 seconds. Make sure you know whether your software is using a rate or a mean parameterization. Also make sure that you're consistent on your time units throughout the program, i.e., don't mix seconds for one item with minutes or hours for other items.

pjs
  • 18,696
  • 4
  • 27
  • 56