Scales for measurement of variables
To measure is to assess, quantify, analyze or appraise. It
is to discover the extent, dimensions, capacity and quantity of any physical
object.
Educational research deals mainly with ideas. “How sound is
an idea” is parallel to assessing “how well you like a song, a painting or
personality of your manager”. While physical objects are measured directly,
ideas or concepts are measured with the help of an operational definition. Four
scales are used to measure any object or to quantify any concept or idea or
properties. These are discussed as follows:
NOMINAL SCALE
It is just a label having no intrinsic value or quality. It
cannot be used in grading or ranking, There are no overlaps and nominal scale
are mutually exclusive. One can be either Muslim or nonMuslim, not both at the
same time as it requires an item to be placed in one and only one class. It is
used for counting or crosstabulation.
Hair could be black or grey, blood can be A, B, O or AB. In
cricket, there is left arm or right arm spinners.
It is used for obtaining personal data and is usually
exhaustive to include all categories or segmentation.
ORDINAL
It used for ranking, rating or grading. It can show best to
worst status or first to last preference. But distance between two ordinal
scales is not the same. Income level of poor, middle and rich class are like
less than Rs.10,000, between Rs.11,000 to Rs.50,000 and 51,000 and above. The
distances are 10,000, 39,000 and infinitive respectively.
It is evident that ordinal scale can rank some items in an
order like less than or more but not “how much more”
INTERVAL
It is more powerful than nominal and ordinal as it not only
orders or ranks or rates but also shows exact distances in between. But it does
not start from zero. If there is zero like zero temperature is not natural but
arbitrary as 0 degree does not mean any temperature. Likewise, year 0 in a
forecast is the end of construction year.
This scale is used in addition or subtraction of scale value
to calculate mean, range, variance, standard deviation, correlation and
regression.
Difference between interval and ordinal scale:
Ordinal scale only ranks but does not measure difference
between the two ranks like “satisfactory” and “notsatisfactory”. Interval
scale not only ranks but also gives exact distance between them by assigning a
value. Difference in temperature of 20 degree and 40 degree is 20 but 40 is not
double hot than 20.
RATIO SCALE
This scale can perform all functions. It can show all
mathematical and geographical indicators. It is useful when exact figures are
required in objective matters are required.
If a person is drawing a salary of Rs.20, 000 and another
Rs.40,000, it can be said that the latter is getting double the salary of the
former.
FOUR SCALES COMPARED
NOMINAL

ORGINAL

INTERVEL

RATIO

Classification but no order,
distance or origin

Classification but order but no
distance or unique origin

Classification, ordered and
distance but no unique origin

Classification, order, distance
and unique origin

Determining of equality

Determination of greater or lesser
value

Determination of equality of
intervals or differences

Determination of equality of
ratios

Only Label

Ranks, Rating and Grade

equal grouping

Weight, height

Gender (male, female)

Doneness of meat, (well, medium
well, medium rare, rare)

temperature in degrees

Age in years

Counting

Frequency Distribution

Addition/subtraction but no
multiplication or division

All functions

Black & While

AAA, BBB, CCC

personality measure

Can say no measurable value like
zero sales

Religion

Levels, onestar & 4star

Mean, range, variance, standard
deviation

Annual Income
