Variables - kopio
The apples I bought cost half of the pears but they were two times tastier.When studying a statistical data, you MUST be aware of what kind of variables are used. For example, program of a university student is usually marked with a number but the average of them does not mean anything.
Figure 2.1. Statistical variables
Categorical variables divide observations in mutually exclusice groups (sex, opinion etc.) For example, the program of a university student is in a nominal scale, as it only divides students according their major. If groups could be sorted in a logical order, the variable is said to be in an ordinal scale. For example, education has a logical order: primary school, secondary school, tertiary level etc.
Numerical variables are naturally real numbers:
- If a property does not disappear at zero, when a variable is in an interval scale (temperature). Ratio of actual values have no meaning.
- If the property "disapper" with the values 0, the variable is in a ratio scale. Ratio of actual values has a meaning: an object A of 15 kg, an object B of 45 kg => the object B on 3 times heavier than the object A. The unit of variables in an interval or in a ratio scale is not fixed.
- If the variable behaves like in a ratio scale BUT the unit is fixed, when the variable is in an absolute scale (the number of people).