EXAMPLE 2.2 Inventory and Sales

Emily is a district manager for a retail chain. She wants to know how the average monthly inventory and monthly sales for the stores in her district are related to each other. Emily doesn't think that either inventory level or sales explains the other. She has two related variables, and neither is an explanatory variable.

Zachary manages another district for the same chain. He asks, “Can I predict a store's monthly sales if I know its inventory level?” Zachary is treating the inventory level as the explanatory variable and the monthly sales as the response variable.