Qualitative property

Qualitative properties are properties that are observed and can generally not be measured with a numerical result.^[1] They are contrasted to quantitative properties which have numerical characteristics.

Some engineering and scientific properties are qualitative. A test method can result in qualitative data about something. This can be a categorical result or a binary classification (e.g., pass/fail, go/no go, conform/non-conform). It can sometimes be an engineering judgement.

The data that all share a qualitative property form a nominal category. A variable which codes for the presence or absence of such a property is called a binary categorical variable, or equivalently a dummy variable.