Editing Level of measurement (section)

=== Ratio scale ===
:''See also'': {{section link|Positive real numbers#Ratio scale}}

The ratio type takes its name from the fact that measurement is the estimation of the ratio between a magnitude of a continuous quantity and a [[unit of measurement]] of the same kind (Michell, 1997, 1999). Most measurement in the physical sciences and engineering is done on ratio scales. Examples include [[mass]], [[length]], [[Time|duration]], [[plane angle]], [[energy]] and [[electric charge]]. In contrast to interval scales, ratios can be compared using [[division (mathematics)|division]]. Very informally, many ratio scales can be described as specifying "how much" of something (i.e. an amount or magnitude). Ratio scales are often used to express an [[order of magnitude]] such as for temperature in [[Orders of magnitude (temperature)]].

==== Central tendency and statistical dispersion ====
The [[geometric mean]] and the [[harmonic mean]] are allowed to measure the central tendency, in addition to the mode, median, and arithmetic mean. The [[studentized range]] and the [[coefficient of variation]] are allowed to measure statistical dispersion. All statistical measures are allowed because all necessary mathematical operations are defined for the ratio scale.