The data should indicate the number of items shipped and returned in each period
The data should track the number of systems shipped and the number of systems returned from the shipment in subsequent time periods. For example, an automobile company tracks the total number of cars shipped each year and the number of cars returned each year from each annual shipment.
The data should be in triangular matrix form
When the number of returns for each shipment are recorded for each subsequent period, the rows or columns of data for shipments that occur in earlier time periods are longer. As a result, the data in the worksheet will appear in the form a triangular matrix, with the shortest rows or columns of data associated with the most recent shipments. For more information on how the data appear in a triangular format, go to Enter your data for Pre-Process Warranty Data.