**Measurable characteristics can be termed as Quantitative Characteristics.**

**Quantitative Characteristics are called as Variables.**

**Non-Measurable characteristics can be termed as Qualitative Characteristics.**

**Qualitative Characteristics can be called as Attributes.**

**Attributes types can be Positive or Negative.**

**Positive Attributes are denoted as "A", "B", "C"....**

**Negative Attributes are denoted as "α", "β", "γ"....**

**Attributes themselves represent a Group. Such groups can be termed as "Classes"**

**Positive Attributes can have Positive Frequencies and Negative Attributes can have Negative Frequencies. **

**Invalid classes can be "A" and "α"; "B" and "β"; "C" and "γ" **

**Relationship of Frequency can be studied in the Contingency Table.**

**Contingency Table can be for 2 OR 3 Attributes.**

**Contingency Table for 2 Attributes is also termed as 9 Square Table or 2 x 2 Table.**

**Any class frequencies cannot be greater than total population. Hence each class frequency must be less than or equal to "N"**

**Any class frequencies cannot be negative. Hence each class frequency must be greater than or equal to 0.**

**9 square table can be used to check consistency of data for 2 attributes. **

**Two attributes are said to be independent if there does not exist any kind of relation between them.**

**Two attributes are said to be associated if they are not independent i.e. they are related in some way or another.**

**Association of Attributes can be Positive or Negative.**

**When two attributes are present or absent together in the data then the attributes are positively associated.**

**When the presence of one attribute is associated with the absence of the other attribute then the attributes are negatively associated.**

**Yule computed another coefficient called coefficient of colligation (γ)**

**Yule's coefficient of colligation is generally restricted to 2 x 2 tables.**