A simple contingency table example, "Shopping Frenzy".

1. Shopping Frenzy
Contingency Table Example
JC Penney Aeropostale American Eagle Macy's Total
Handbags 3 1 2 5 11
Shoes 2 0 0 4 6
Jewelry 2 3 1 6 12
Clothes 7 3 6 2 18
Total 14 7 9 17 47
Mary went on a shopping frenzy and bought handbags, shoes, jewelry and
various clothes at four stores. Using the above contingency table, let's
answer some probability questions.
First we must state that we are pretending these are 47 separate purchases
and that all have the same probability of being selected.
P(Mary bought shoes) 6/47 or 0.1277 (Decimal)
P(Mary bought at Macy's) 17/47 or 0.3617 (Decimal)
P(Mary bought Jewelry at Aeropostale) 3/47 or 0.0638 (Decimal)
P(Mary bought Shoes or something from Macy's) 19/47 or 0.4043 (Decimal)
P(Mary bought clothes given that she shopped AE) 6/9 or 0.6667 (Decimal)
P(Mary shopped Macy's given she bought Handbags) 5/11 or 0.4545 (Decimal)