Measuring performance is the stepping stone to performance analysis. As we noted earlier in this book, there are several performance parameters to be measured with respect to various scenarios. Clojure's built-in time macro is a tool to measure the amount of time elapsed while executing a body of code. Measuring performance factors is a much more involved process. The measured performance numbers may have linkages with each other that we need to analyze. It is a common practice to use statistical concepts to establish the linkage factors. We will discuss some basic statistical concepts in this section and use that to explain how the measured data gives us the bigger picture.