A Guide to Business Statistics

Chapter 3Descriptive Statistics

During my second semester teaching undergraduate statistics, I started one of the classes by presenting the following quote: “the average person has one breast and one testicle.” I did not discuss the statistic, it was simply displayed on the screen while I prepared materials for the class. When this particular class finished, a slightly timid male student came to the front of the room to talk with me. The class had over 90 students in it, so he first introduced himself. And then, he told me how shocked he was to learn that the average person has only one testicle, and before I could reply he shared that he had one of his testicles removed when he was younger. He finished with “I didn't know it was that common.” I paused for a second to figure out how to break the news to him gently. I told him that while the statistic seems to be odd at first, since the gender divide between humans is roughly 50–50, it is a sensible rough estimate. Most men do have two testicles, and since most women have zero, on average people have one. I told him that I introduce this statistic because it gets students thinking about what the average tells us and how in some circumstances the average can be tremendously misleading. From the color of his face, I knew he understood. He and I would later joke about it throughout the semester.

The average, or mean, is what we call a descriptive statistic. Descriptive statistics are the topic for this chapter. In Chapter 2, we ...