Nithisha Khasnavis - 3 years ago 133
R Question

# Mean of a Poisson Distribution Using R's rpois function

I entered the following command in R:

``````my_pois <- replicate(100,rpois(5,10))
``````

I believe this creates 100 sets of 5 numbers in which each set should have a mean of 10. However when I look at the mean of each column(set created), this is what I get:

``````[1] 10.8  9.4  9.0 11.2 11.6 11.6  7.8 12.4  9.6 11.0  9.6  9.8 10.0  8.6  9.8  8.6  9.4
[18] 11.4 12.0  8.4 10.2 10.2 10.8 10.2  7.6  9.8  8.4 10.6 11.6  8.6  9.6 11.0 11.0 10.0
[35]  9.8  9.2  8.2  8.2 10.2  9.0 10.4  9.2 10.4 10.0 11.8 13.8 10.2  9.8 12.4 10.4  9.8
[52]  9.8  8.6  7.4  9.2  9.0  7.4  9.2  9.4 11.8  9.2  9.8 11.6  9.8 10.8  8.6 12.4 10.4
[69]  9.4  9.4  9.0 11.2 10.6  9.4  9.6  8.2  9.6 10.6 10.6  8.2  9.2 10.0 11.2  9.0  9.6
[86] 10.4  8.0 10.2  9.8  7.4  9.6  9.0  7.2  8.4 11.8 10.8  9.4 12.4 11.2 12.0
``````

Shouldn't they all be 10 since we specified a mean of 10?

``````  k <- apply(my_pois,2, function(x) mean(x))