A method for making an inference based on cumulative data. The method utilizes video, audio, and biometric devices to observe a retail environment for the presence of a customer. Once a customer is present, the method identifies every cohort to which the customer corresponds. Next, the method observes the customer as they peruse aisles in the retail environment. When the customer selects a product, the method identifies the selected product and searches the cohorts for alternate products to offer the customer. The method offers one alternate product to the customer and records to the cohorts whether the customer thereinafter accepts the method's offer and selects the alternate product or rejects the method's offer and continues perusing the retail environment aisles. The method continues observing the customer and offering alternate product until the customer leaves the retail environment.