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Removed weird qualification from a dubious source. Counting is a form of measurement, so counting cannot be contrasted with measurement. Moreover, counting doesn't necessarily produce discrete data (e.g., I can count 4 and a half of something). Tag: references removed |
→Discrete variable: Not all discrete variables are count variables. For example, a discrete rating scale from 1 to 5. Or shoe size that only comes in wholes and halves. |
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==Discrete variable==
In contrast, a variable is a '''discrete variable''' if and only if there exists a one-to-one correspondence between this variable and a subset of <math>\mathbb{N}</math>, the set of [[natural numbers]].<ref>{{cite book |last1=Odifreddi |first1=Piergiorgio |title=Classical Recursion Theory: The Theory of Functions and Sets of Natural Numbers |date=February 18, 1992 |publisher=North Holland Publishing Company |isbn=978-0444894830 |page=18}}</ref> In other words, a discrete variable over a particular interval of real values is one for which, for any value in the range that the variable is permitted to take on, there is a positive minimum distance to the nearest other permissible value. The
Methods of calculus do not readily lend themselves to problems involving discrete variables. Especially in multivariable calculus, many models rely on the assumption of continuity.<ref>{{cite book |last1=Clogg |first1=Clifford C. |last2=Shockey |first2=James W. |title=Handbook of Multivariate Experimental Psychology |date=1988 |publisher=Springer Publishing Company |___location=Boston, Massachusetts |isbn=978-1-4613-0893-5 |pages=337–365}}</ref> Examples of problems involving discrete variables include [[integer programming]].
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