Measures are used to quantify size, quantity, intensity, or other characteristics of a physical object. It is a cornerstone of trade, science, technology and quantitative research in many disciplines.
Most modern measurements are based on the International System of Units, which reduces all physical quantities to a mathematical combination of seven base units. This system is referred to as metrology.
Measurement
1. Measurement is the quantification of attributes that allow comparisons of objects and events. It is a cornerstone of trade, science, technology and quantitative research in many disciplines. Measurements are also critical to construction and other technical fields and everyday activities. The scientific study of measurement is known as metrology.
A central line of inquiry in measurement theory concerns the axiomatization of empirical structures. This has yielded results showing that certain kinds of magnitudes-such as length, area, volume, duration and weight-are measurable. These are characterized by the fact that they admit of non-arbitrary ordering and concatenation (addition, multiplication and division). Campbell termed them fundamental.
Measurement is usually performed by comparing a quantity with a standard or reference. This comparison cannot be perfect, and thus measurements include error, a random and systematic deviation from the true value of the quantity being measured. Several different error metrics can be used to evaluate the errors in measurements. There are also a number of other philosophical issues about measurement, such as the metaphysical nature of quantities and epistemological issues concerning the knowledge of quantities.
Units
Units of measurement are used to compare physical quantities. Historically, many different systems of units existed, but they are now all reduced to the seven base units of the International System of Measurement, known as the SI, or metric system. These are based on artifact-free definitions which link each measurement to a physical constant or invariable phenomenon, rather than to a particular standard object that is prone to damage and deterioration. The science of developing and maintaining these nationally and internationally accepted standards is called metrology.
Some of the basic SI units are metre (length), second (time), candela (light brightness), kilogram (mass), kelvin (temperature) and mole (the number of particles in a sample). Combining these creates derived SI units that describe more complex properties. A valid conversion factor converts any unit into any other unit. For example, 1 meter is equal to 10 meters. However, adding two lengths of different units, such as 10 km and 20 m, makes no sense, because they are not the same units.
Uncertainty
Uncertainty is a central concept in measurement, and it’s important to understand how to measure uncertainty. It’s important to recognize uncertainty triggers in yourself, too – like over-worrying or pessimistic thinking. You can also get uncertainty triggers from outside yourself – like reading news stories that focus on worst-case scenarios.
Heisenberg’s uncertainty principle demonstrates that even the most careful and rigorous scientific investigations cannot yield an exact value for a quantity. Instead, repeating an investigation will produce a scatter of measurements distributed around some central value. This scatter is caused by human and instrument errors, as well as natural variability in the phenomena being measured.
To be considered a measure, a set must satisfy two subcriteria: coherence, or the consistency of measurement outcomes with relevant background theories or other substantive presuppositions; and objectivity, or the mutual consistency of measurement outcomes across different measuring instruments, environments and models. Moreover, any measure must be measurable, or at least, it must be a countably additive set function.
Metrics
Metrics are a quantitative way to monitor the progress and status of specific processes. They help enhance your decision-making process by enabling you to identify areas where your business needs to improve and quantify the success of those efforts.
A metric is an aggregated measurement of data in a table and it’s a type of calculated column. It uses an aggregation function (SUM, AVERAGE, MAX, etc) to sum or average the values of its parent rows. It also takes into account filter contexts like slices, columns and rows to determine its results.
The main advantage of measures is that they are not memory-hungry, unlike calculated columns. However, they are limited by their scope – they are only a snapshot in time and their results can be misleading, especially when the calculation is highly dependent on a filter context. Hence, it’s better to use calculated columns when you need flexible calculations that change with user actions and don’t require the aggregation of data from multiple tables.