Working With Sample Data

Chapter 3

Understanding the Normal Distribution and the t-Distribution

If you have ever watched someone sift flour in a kitchen or dig a hole and pile the dirt in the same place outside, you have seen a normal distribution, albeit somewhat imperfect. It is bell shaped, symmetric, peaked in the center with tails that trail off rapidly the greater the distance from the center. While imperfect versions of the normal distribution are easily seen in ordinary life, its discovery is credited to the great German mathematician Johann Carl Friedrich Gauss (1777–1855), who documented that errors of routine measurements often follow a normal distribution. Some normal distributions can be huge, as seen in a pile of hulls at the end of a dump chute from an ...