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		Values have any meaningful order	Distance between values is defined	Mathematical operations make sense (Values can be used to perform mathematical operations)			There is a meaning ful zero-point	Values can be used to perform statistical computations					Example
				Comparison operators	Addition and subtrac tion	Multiplica tion and division		"Counts", aka, "Fre quency of Distribu tion"	Mode	Median	Mean	Stn
Nominal	Values serve only as labels	colspan="11" style="margin: 0; padding: 0;" ✘ ✘ ✘ ✘ ✘ ✘ ✔ ✔ ✘ ✘ ✘ Values don't have any meaningful order No distance between values is defined Values don't carry any mathematical meaning Values cannot be used to perform many statistical computations, such as mean and standard deviation	For an attribute "outlook" from weather data, potential values could be "sunny", "overcast", and "rainy".
Ordinal	Distinction between nominal and ordinal not always clear (e.g., attribute "outlook")	✔ ✘ ✔ ✘ ✘ ✘ ✔ ✔ ✔ ✘ ✘ Values have a meaningful order No distance between values is defined Comparison operators make sense Mathematical operations such as addition, subtraction, multiplication, etc. do not make sense											An attribute "temperature" in weather data with potential values fo: "hot" > "warm" > "cool"
Interval		✔ ✔ ✔ ✔ ✘ ✘ ✔ ✔ ✔ ✔ ✔ Distance between values is defined. In other words, we can quantify the difference between each value Comparison operators make sense Addition, subtraction, make sense Multiplication, and division do not make sense Interval variables often do not have a meaningful zero-point. (not sure)											An example of an interval variable would be temperature.  We can correctly assume that the difference between 70 and 80 degrees is the same as the difference between 80 and 90 degrees.  However, the mathematical operations of multiplication and division do not apply to interval variables.  For instance, we cannot accurately say that 100 degrees is twice as hot as 50 degrees. Additionally, interval variables often do not have a meaningful zero-point.  For example, a temperature of zero degrees (on Celsius and Fahrenheit scales) does not mean a complete absence of heat.
Ratio		✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ All arithmetic operations are possible on a ratio variable Ratio variables have a meaningful zero-point