Values can only be calculated in natural numbers or integer units, and their values are discontinuous, and there are no other values between two adjacent values. The value of this variable is usually obtained by counting.

Continuous variable (continuous)

You can take any value in an interval, and its value is continuous. Two adjacent values can be divided infinitely, that is, they can take infinite values. Such as height, length of rope and so on.

Compared with discrete variables, continuous variables have the concept of true zero, so they can be multiplied and divided.

Classification variables can be divided into the following two categories:

Ordered classification variable (ordinal number)

Describe the rank or order of things. Variable values can be numeric values or characters, which can further compare the advantages and disadvantages, such as the degree of liking: like it very much, like it generally, and dislike it.

Disordered classification variable (nominal)

There is no order difference between numerical values, which can only be classified into binary variables and multi-classification variables. Binary variables refer to dividing all data into two categories, such as male, female, right, wrong, yin and yang, etc. Binary variable is a special classified variable and has its own unique analysis method. Multi-classification variables refer to more than two categories, such as blood types divided into A, B, AB and O.

The difference between ordered classified variables and unclassified variables is that the former is meaningful for comparison operation, while the latter is meaningless for comparison operation.