6. MEASUREMENT AND SCALES

1. Measurement:

The concept of measurement:    Defined as the assignment of numbers to characteristics of objects, persons, states or events according to rules.

Scales of measurement: THE GOAL:  Assign numbers so that the properties of the numbers are paralleled by the properties of the events or objects we are measuring.

2. The four measurement scales NOIR

1) Nominal: composed of numbers used primarily to categorize objects or events with two rules:

a) all members of a class have the same #

b) the classes are mutually exclusive

2) Ordinal: represent numbers used to rank items.

ordinally scaled numbers preserve rank orders but not differences.

3) Interval: represent numbers used to rank items such that numerically equal distances on the scale represent equal distances in the property being measured.  The location of the zero point is arbitrary.

4) Ratio:  represent numbers used to rank items such that numerically equal distances on the scale represent equal distances in the property being measured.  The location of the zero point is fixed.

3. scaling：

1) Rating Scales:

- Non-comparative (Graphic and itemized)

- Comparative (Graphic and itemized)

- Paired comparison

- Constant sum scale

2) Some Famous Scales:

- Semantic Differential

- Stapel

- Likert

- Thurstone Law of Comparative Judgment