Users are incredibly valuable. They offer a depth of insight into their experiences and motivations, not just what they do but why. There's a catch though - in fact many catches. Qualitative (descriptive) data from user research only sampled from a few people. Usually those people are roughly approximation of your true user base : they speak your language, live near you, have free time in the middle of the day to participate in research. There's often a huge gap between what people say they will do or how they will behave when they're being watched, and what they actually do. This is where quantitative (numerical) data comes into play. As a PM, you need to use quantitative data and metrics to learn what people actually do, identify new opportunities and measure success.

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