Categorical Predictor Variables in Design of Experiments (DOE)

Inputs to designed experiments can fall into two general broad categories: Quantitative and Categorical (Qualitative). Quantitative inputs have scale or a direction measurement such as temperature and pressure. Categorical variables do not have scale – examples include vendor, day of week, and color. It is important to note that while you can assign a number… Read More

Logistic Regression Case Study Did Performance-Enhancing Drugs Favor Batters or Pitchers?

My previous article analyzing the performance of Barry Bonds and Roger Clemens has spurred quite a controversy. In the article, the statistics show that Roger Clemens’ performance was not statistically improved during the alleged performance-enhancing drug years. I often get comments from baseball fans; many of them are not swayed by the data. They are… Read More