Adjustment in class interval
Also called: Class boundaries · Topic: Economic Data: Census, NSS, Surveys and Statistical Tools · NCERT: Class 11, Ch 3 "Organisation of Data"; Class 11, Ch 4 "Presentation of Data"
Meaning
The adjustment in class interval makes inclusive classes continuous. In inclusive classes, both limits belong to the class, so there are gaps between classes (for example, between 899 and 900). To close the gaps, find half the gap between one class's upper limit and the next class's lower limit. Subtract it from every lower limit and add it to every upper limit. The adjusted limits are called class boundaries. Continuous data need these boundaries before they are drawn as a histogram.
Example
The classes are 800-899, 900-999 and so on. The gap is 900 − 899 = 1, so half the gap is 0.5. The class 800-899 becomes 799.5-899.5, and 900-999 becomes 899.5-999.5.
Don't confuse with
- Exclusive method: in classes such as 10-20, 20-30, the upper limit goes to the next class. These classes are already continuous and need no adjustment.
Related concepts
- Raw data
- Classification
- Chronological classification
- Spatial classification
- Qualitative classification
- Quantitative classification
- Attribute
- Continuous variable
- Discrete variable
- Frequency