From supposed weights of batches
of unequal sizes of bags (or any other collective items),
points to the determination of the mean and standard deviation,
μ and σ, of the Gaussian distribution
of the weight of the individual item (bag, in the example).
The sample (indeed, commercial lot) sizes are Ni,
i = 1..n, given in the vector N.
This is an attempt to estimate σ
(estimating μ is obvious) from a set of experimental data
that: are here simulated; but routinely exist in many industries.
(The base data are inspired in real bags of fertilizers.)
Draws a simple plot of the overall average
and the batches' averages. | 
