Metrics are the measurements that reduce uncertainty
A metric is a quantitative measurement or a few measurements of something in some specific context. The purpose of any metric is to help decision-makers make better decisions. The difficulty of making a decision is that usually there is some uncertainty associated with the decision. We use metrics to reduce that uncertainty. Metrics do not need to reduce uncertainty to zero, but they must add some additional information about a phenomenon or information that simplifies understanding of the phenomenon.
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