Cumulative frequency
Also called: Less than cumulative frequency, More than cumulative frequency · Topic: Economic Data: Census, NSS, Surveys and Statistical Tools · NCERT: Class 11, Ch 4 "Presentation of Data"; Class 11, Ch 5 "Measures of Central Tendency"
Meaning
Cumulative frequency is the running total of frequencies. A "less than" cumulative frequency adds frequencies from the lowest class upward. A "more than" cumulative frequency adds them from the highest class downward. When cumulative frequencies are plotted, the graphs are called ogives. The two ogives cross at the median. Cumulative frequency is also used to find the median and quartiles with a formula.
Example
In NCERT's marks table for 100 students, the "less than" cumulative frequencies are: less than 10: 1; less than 20: 9; less than 30: 15; less than 40: 22; less than 50: 43; less than 60: 66. The 50th student falls in the 50-60 class, so that class holds the median.
Don't confuse with
- Class frequency: the count in one class alone (23 in the 50-60 class), not a running total.
Related concepts
- Raw data
- Classification
- Chronological classification
- Spatial classification
- Qualitative classification
- Quantitative classification
- Attribute
- Continuous variable
- Discrete variable
- Frequency