Information Value of Summary Data
The information value of summary data is extremely limited. As we have seen, summary data cannot answer questions about daily sales patterns by store, nor can it reveal what additional purchases were made in the same market basket, nor can it tell you anything at all about the individual customer who made the purchase.
What summary data can provide is summary answers and nothing more. This puts you in the position of always being reactive rather than proactive. Two classic retail dilemmas posed by this summary-only situation indicate that both extremes of a given problem can be caused by only having access to summary data: