Ellen Heemer in Houston, Texas, writes:
You said that cards need to be shuffled seven times to be adequately mixed. How did you come to that conclusion? My bridge friends don’t quite believe this.
Marilyn responds:
I said that studies indicate that seven ordinary shuffles are best in a practical sense. Fewer aren’t quite sufficient for a random mix, and more shuffling doesn’t help enough to be worth the time or effort. The original, now-famous study was done by mathematicians Dave Bayer (Columbia University) and Persi Diaconis (Harvard University) back in 1992. Here’s a link to the paper (http://statweb.stanford.edu/~