There are 4 types of variables namely nominal, ordinal, interval & ratio. These are further classified as qualitative and quantitative.
Qualitative – Nominal & Ordinal
Quantitative – Interval & Ratio
Nominal Variables
Also called as discrete/qualitative or categorical variables. These can only me used for qualitative classification. Categories can be 2 or more but lack any order or rank.
Eg. – Nationality – Indian/British/American
Gender – Male/Female
Blood Type – A/B/O/AB
We cannot apply any mathematical or logic operation except “=” & “not =” on these variables.
Ordinal Variables
These are similar to nominal but the categories in this case are ordered/hierarchical. But the severity od answer cannot be measured as a value. But it can be rated on some scale like on scale of 1 to 5 or 1 to 10 or any other hypothetical scale to give a fair idea.
Example: Stage of a disease – Stage I, II, III, IV
Health Status – Fine, Very healthy, sick, very sick
Satisfaction level – Neutral, satisfied, very satisfied
Mathematical operation of “<“,”>”,”=” and “not =” can be applied.
Interval Variable
These allow clear comparison by means of two or more numerical values. These values have constant and equal difference between them but the zero point is arbitrary.
For example – Temperature difference, say temp. on Monday was recorded to be 20 degree and on Tuesday to be 40 degree Celsius, on the basis of these values we can clearly identify that Tuesday was hotter then Monday but cannot conclude that it was twice hot then Monday as 0 degree Celsius is not the actual zero point or starting point of temperature scale.
Only two mathematical operation of multiplication and division cannot be applied on these variables.
Ratio Variables
These variables have equal interval between their values and zero point plays important role and is meaningful. These are one of the most commonly used variables in daily life in form of length, time, weight and similar units.
Eg. Weight – 20 Kg, 40 Kg, 100 Kg
We can say that 40 Kg is twice heavier then 20 Kg
length – 2 m, 5 m, 10 m, 5 Km
All logic/mathematical operation can be applied on these variables.
