When clients want to get started with metrics, they often have questions. How can we use metrics to manage testing? What metrics can we use to measure the test process?  What metrics can we use to measure our progress in testing a project?  What do metrics tell us about the quality of the product? We work with clients to answer these questions all the time. In this article, and the next three articles in this series, I'll show you some of the answers.

Why Should We Have Metrics?

Sometime I hear people asking why metrics are necessary, or worse yet disparaging metrics with smug comments like: "Not everything that you can measure matters, and not everything that matters can be measured." To me, such remarks are like questioning the value of literacy, or saying that reading is unimportant because you don't need to read to appreciate good art. 

Metrics allow us to measure attributes. Metrics allow us to understand. Metrics allow us to make enlightened decisions. Metrics allow us to know whether our decisions were the right ones, by assessing the consequences of those decisions. Metrics are rational. 

Plus, you really don't have much alternative to metrics usage.  The other option is to base your understanding, decisions, and actions on subjective, uninformed opinions.  This is not a sound basis for management.

You might be thinking; "I'm a reasonable person, and I make all sorts of smart and reasonable decisions in my everyday life without metrics."  Well, maybe.  First off, you might have grown so accustomed to all the metrics we have around us that you didn't notice them. When we drive, we refer constantly to a key metric: speed.  When we shop, we mostly use the metric of price. In many situations, when you find yourself without the usual metrics, you might feel lost.

Second, when people make decisions or reach conclusions without metrics, based on what sounds reasonable, they can be wrong. My favorite example of this comes from the Greek philosopher, Aristotle. Aristotle was a smart fellow, and he said a lot of smart things. However, he also said that heavier objects fall faster than lighter objects. 

That sounds reasonable, and anecdotal evidence like feathers and stones are all around us. Two thousand years later, though, Galileo dropped two cannonballs of very different weights from the Leaning Tower of Pisa. Both hit the ground at the same time.  Simple experiment. Simple metric. Two thousand years of misguided thought overturned with a single thud.