Usually, when people discuss measurements they speak in absolute terms—degrees of temperature, millimeters of length, ounces of weight, candela of illumination intensity, degrees of angle, etc. For example, when I say the temperature is 56.4° F, the implicit understanding is that there’s direct correlation and agreement with a standard. This makes the temperature measurement meaningful when shared with others who know the Fahrenheit scale. In other words, a reading of 56.4° F represents a specific temperature that would match a reading of 56.4°F taken anywhere else in the world. But how do you know it really matches?Meaningful measurement systems

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