Page 38 - DEDU504_EDUCATIONAL_MEASUREMENT_AND_EVALUATION_ENGLISH

Educational Measurement and Evaluation

Notes 3.1 Concept of Scales of Measurement
Any test can be useful only when it is reliable, and it should be able to measure only that
attribute or characteristic for which it has been constructed. The tools for measurement have been
needed from ancient times, and we need them in our daily life.
The basis of educational measurement are data. Whatever the type of measurement-physical,
social, economic or psychological, it is necessary to gather data. From the viewpoint of convenience,
we place the available data into four levels. These four levels are arranged in a definite order.
The lower level can be easily measured, but the measurement done by it will be under some
doubt. On the contrary, measurement in the higher level is more complex, but the inferences
drawn from it will be more accurate. Thus, accuracy of measurement depends on its level.
Generally, individuals, objects, events, observations and characteristics are given a quantitative
form under the measurement process. Measurement Scales are used to categorize or quantity
variables. In essence, each scale has a single objective, and its rules, theory, characteristics,
limitations and statistical techniques are different from other levels fully.
Measurement has the following four chief levels :
1. Nominal scale.

2. Ordinal scale.
3. Interval scale, and
4. Ratio scale.

3.2 Properties of Measurement Scales

Each scale of measurement satisfies one or more of the following properties of measurement.
• Identity : Each value on the measurement scale has a unique meaning.
• Magnitude : Values on the measurement scale have an ordered relationship to one another.
That is, some values are larger and some are smaller.
• Equal intervals : Scale units along the scale are equal to one another This means, for example,
that the difference between 1 and 2 would be equal to the difference between 19 and 20.
• Absolute zero : The scale has a true zero point, below which no values exist.
Values assigned to variables represent a descriptive category, but have no inherent numerical
value with respect to magnitude.
Gender is an example of a variable that is measured on a nominal scale. Individuals may be
classified as “male” or “female”, but neither value represents more or less “gender” than the
other. Religion and political affiliation are other examples of variables that are normally measured
on a nominal scale.

The ordinal scale has the property of both identity and magnitude. Each value on the
ordinal scale has a unique meaning, and it has an ordered relationship to every other
value on the scale.

3.3 Nominal Scale

This is the lowest level of measurement. Some people call it by the name of classification level
too. Under this scale, the measured objects or events are classified into separate groups on the

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