Interval Scale
Interval data possesses all the properties of ordinal scale with one additional property. This property is that the differences between the various levels of the categories on any part of the scale reflect equal differences in the characteristics measured. That is, equal unit is established in the scale (sometimes referred to as equal unit scale).
An example of interval scale is temperature. The properties of interval data are as follows:
1. data categories are mutually exclusive
2. data categories have some logical order.
3. data categories are scaled according to the amount of the particular characteristics they possess.
4. equal differences in the characteristics are represented by equal differences in the numbers assigned to the categories.
5. the point zero is just another point on the scale.
Ratio Scale
The highest level in the hierarchy of measurement scale. The scale has one property in addition to the properties listed above for the interval scale. This property is a known or true zero point that reflects an absence of the characteristics measured. Examples of ratio scales are income, age, weight, height, score, etc.
The properties of ratio data are as follows:
1. data categories are mutually exclusive
2. data categories have some logical order.
3. data categories are scaled according to the amount of the particular characteristics they possess.
4. equal differences in the characteristics are represented by equal differences in the numbers assigned to the categories.
5. the point zero reflects an absence of the characteristic.
