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I heard that the number of meteorites of the given size that hit the Earth follows the Poisson distribution. I am wondering how to estimate the Poisson parameter $\lambda$ and its 95% c.i. if I have only one measurement for a given meteorite size.

Let's propose that we are considering 100 year period of time. For that period of time, we observed $k=5$ meteorites with a diameter greater than 1 meter.

Two ideas came into my mind about how we can estimate $\lambda$.

A. First is to use the formalism described here: Determining confidence interval with one observation (for Poisson distribution) So we will get that (for 95%): $$ \hat{\lambda}_\mathrm{MLE} = 4\\ 95\%\,\, \mathrm{c.i.}: (k+2-1.96\sqrt{k+1},k+2+1.96\sqrt{k+1}=\\ (1.6,10.4) $$ B. The second idea is to fix $k=4$ and calculate the probability that true $\lambda$ will appear in interval from $\lambda_1$ to $\lambda_2$: $$P(\lambda_1<\lambda<\lambda_2)= \int_{\lambda_1}^{\lambda_2}f(k=4,\lambda)d\lambda $$ where $f$ is Poisson PMF. From here, taking $\lambda$ in range from 0.1 to 10 with step 0.1 I can estimate the median value and 95% c.i., which will be: $$\lambda_\mathrm{median} = 4.6\\ 95\%\,\, \mathrm{c.i.}: (1.9,9) $$ My question is: are both estimations (A and B) okay?

An additional question is can I use the same estimations if I consider some big number of small meteorites ($k=50$) or $k=0$ if we consider super-big meteorites.

SerKo
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    Also worth looking at https://stats.stackexchange.com/questions/15371/how-to-calculate-a-confidence-level-for-a-poisson-distribution where one of the answers points to 19 different approaches to a Poisson confidence interval – Henry Mar 15 '22 at 13:01
  • If you observe $0$ cases, the rule of three suggests a 95% confidence interval for the parameter of $[0,3]$ – Henry Mar 15 '22 at 13:50
  • You seem to be constructing two different intervals: the first appears to be an attempt at an (approximate) confidence interval while the second is a kind of tolerance interval. Could you therefore please explain what you want this interval to represent? – whuber Mar 15 '22 at 15:28
  • @whuber I am trying to represent the interval that will include the true value of $\lambda$ with 95% probability. Please forgive me if that sounds not statistically right. After your question, I googled what does confidence and tolerance intervals mean, and looks like I need c.i., however, I did not understand fully what is the difference between tolerance and confidence in the application to my question. – SerKo Mar 15 '22 at 15:49

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