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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 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