Calculates the risk that at least one person in a group has Covid:

Number of persons in the group:
The chance of at least one infected member is %.
For this calculation we assume that a person is infective for roughly seven days, and
that the incidence - the number of registered infections within the last seven days person
100.000 - is a near enough approximation to this. If you have other assumptions, just
adjust the incidence to the number of infected per 100.000 you assume.

Another assumption is that each member of the population has the same base chance
to be infected, based upon the incidence. This is rarely so, but hard to simulate otherwise.
If you are not happy with this, adjust the incidence or make your own script :-)