Shuffling cards

The analysis of random processes is a familiar duty in life (“How long does it take to get to the airport during rush-hour?”) as well as in mathematics. Of course, getting meaningful answers to such problems heavily depends on formulating meaningful questions. For the card shuffling problem, this means that we have to specify the size of the deck (n = 52 cards, say),to say how we shuffle (we’ll analyze top-in-at-random shuffles first, and then the more realistic and effective riffle shuffles), and finallyto explain what we mean by “is random” or “is close to random.”