Final answer:
The activity involved in determining which probability distribution to use is determining the type of numerical data you are working with.
Step-by-step explanation:
When determining which probability distribution to use to calculate probabilities, the activity involved is determining the type of numerical data with which you are working. This is because different distributions are used depending on whether the data is discrete or continuous and whether it fits certain conditions specific to known distributions like the normal, binomial, or Poisson distributions, among others.