BIOL 205
BIOSTATISTICS
SCALES OF MEASUREMENT
There are four scales of measurement used to measure
any variable.
1. Nominal Scale
2. Ordinal Scale
3. Interval Scale
4. Ratio Scale
1. Nominal Scale
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The most elementary scale
Just identify categories; species, gender, color
No difference could be made by arrangements
Examples are gender – female and male; eye color –
black, brown, green
 For qualitative / categorical variables
2. Ordinal Scale
 Have all the properties of “nominal scale”;
classifying and labeling, for example
 New thing is “a sense of order / arrangements”
 Ordinal numbers / data are used to “rank order”
 For example, DAFOR
Category
Dominant
Abundant
Frequent
Occasional
Rare
Score
5
4
3
2
1
There is no relationship between numerical values of
abundance scale, i.e. Abundant does not mean twice
Occasional
3. Interval Scale
 In addition to classification and ranking, interval
scale allows the recognition of precisely “how far
apart are the individual classes from each other on the
scale”
 The distance between 8th and 9th points on the scale
is the same as that between the 3rd and 4th
 Date is a very widely used interval scale variable
 There is no absolute zero, so, it is not possible to say
that 9th value is 3 times that of 3rd
4. Ratio Scale
 The highest level of measurement
 Incorporates the properties of nominal, ordinal and
interval scales
 Includes an absolute zero, in addition
 All mathematical procedures of +, -, x and / are
possible
 Examples are length and mass; for example, length of
150mm is three times as long as 50mm