In order to learn about how price discounts impact products, a study is done where groups of product types are randomly assigned to have their prices discounted by either 10% or 20%. The product groups vary in size from 5 to 10 products of a similar type, and there are 100 product groups. The study contains 730 products in total. Six months after randomization to a discount level, the average number of monthly purchases within each product group is calculated for each group. The average of these values within the 10% discounted product groups is compared against the average values within the 20% product group to characterize the impact of the varying levels of discount.

Define the units, potential outcomes, and causal estimand underlying this study.