I'm running a bunch of trials, $T$, and the outcome of each trial is some number of objects $k_i$ for $i = [1, T]$. I would like to say something about the average "spread" in terms of the number of objects observed each trial, $k_i$, something like a mean variance. However, since $k_i$ can be equal to one, and I'm not sure that the variance of a single object is well-defined, I am unsure how to proceed.
What is a good metric for measuring the average "spread" of my $k_i$? Is a variance of one object, a "variance of zero", well defined?
Let me provide an example: Say I perform an experiment, and the output of that experiment is some number of cells, $k_i = (1, 2, ...)$. I perform $T = 2$ experiments. One experiment outputs $k_1 = 1$ cell, and the other experiment outputs $k_2 = 2$ cells. What is my mean variance for an experiment (obviously two trials isn't enough)?