First, the hat. It was the winter of 2007, and I had just realized that the chemotherapy I was undergoing for stage 2 breast cancer would render me bald long before my wig was ready. So after one of my infusions, I dropped in on the hospital shop and burrowed through a large basket filled with hats. After trying one on and asking about the price, I learned that all of the hats were free, having been donated by people who wanted to make things a little easier for cancer patients. I gratefully accepted the hat, moved by the fact that a stranger had donated it. I had always pitied Blanche DuBois and her reliance on “the kindness of strangers,” but now I suspected that she recognized a good thing when she saw it. The hat did its job well, keeping me warm and reasonably fashionable until chemo ended. It was spring by the time I moved on to radiation and my hair began to grow back, so I stuffed the hat into the back of my closet and forgot about it. But that trip to the gift shop popped into my mind much later, when I had been cancer-free for five years and was looking for a way to mark this statistically sig …