Scales of Measurement in Research
Scales of measurement refer to the ways in which variables or numbers are defined and categorized in research. Understanding the scale helps determine the type of statistical analysis to use.
There are four main types of scales, each with increasing levels
of precision and statistical power:
1. Nominal Scale (Categorical Data)
- Definition:
Categorizes data without any order or ranking.
- Nature:
Qualitative
- Examples: Gender
(Male, Female), Blood Group (A, B, AB, O), Religion, Marital Status
Feature |
Description |
Order |
❌ No inherent order |
Arithmetic Ops |
❌ Not possible |
Statistics |
Frequency, Mode |
2. Ordinal Scale (Rank Order)
- Definition:
Categorizes data with a meaningful order, but differences
between ranks are not equal.
- Examples: Customer
satisfaction (Poor, Fair, Good, Excellent), Socioeconomic status (Low,
Middle, High), Education level
Feature |
Description |
Order |
✅ Yes |
Difference |
❌ Not measurable or equal |
Statistics |
Median, Percentile, Rank Order |
3. Interval Scale
- Definition: Ordered
data with equal intervals between values, but no true zero point.
- Examples:
Temperature in Celsius or Fahrenheit, IQ scores, Calendar dates
Feature |
Description |
Order |
✅ Yes |
Equal Interval |
✅ Yes |
True Zero |
❌ No |
Statistics |
Mean, SD, Correlation |
4. Ratio Scale
- Definition: Like
interval scale but with a true zero point, allowing for the
calculation of ratios.
- Examples: Weight
(kg), Height (cm), Age (years), Income (₹), Sales volume
Feature |
Description |
Order |
✅ Yes |
Equal Interval |
✅ Yes |
True Zero |
✅ Yes |
Statistics |
All (Mean, Mode, Median, SD, Ratio) |
Summary Table
Scale |
Type |
Order |
Equal Interval |
True Zero |
Examples |
Allowed Statistics |
Nominal |
Qualitative |
❌ |
❌ |
❌ |
Gender, Religion |
Mode, Frequency |
Ordinal |
Qualitative |
✅ |
❌ |
❌ |
Rank, Satisfaction Level |
Median, Percentile |
Interval |
Quantitative |
✅ |
✅ |
❌ |
Temperature (°C), IQ |
Mean, SD, Correlation |
Ratio |
Quantitative |
✅ |
✅ |
✅ |
Weight, Income, Age |
All statistics, including Ratios |
Importance in Research
- Determines
statistical tools to be used (e.g., t-test requires interval or
ratio scale).
- Influences
data interpretation and validity.
- Helps
design appropriate questionnaires and scales.
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