Frequency distribution
Topic: Economic Data: Census, NSS, Surveys and Statistical Tools · NCERT: Class 11, Ch 3 "Organisation of Data"; Class 11, Ch 4 "Presentation of Data"; Class 11, Ch 8 "Use of Statistical Tools"
Meaning
A frequency distribution is a table that sorts the values of a quantitative variable into classes. It shows how many observations fall in each class. That count is called the class frequency. It turns a heap of raw numbers into a picture of how the values are spread: where most of them sit, and where only a few lie. Each class has class limits (its lower and upper ends) and a class mark, its midpoint: (upper limit + lower limit) ÷ 2. Averages, histograms and ogives are all built from this table.
Example
NCERT's marks of 100 students give this table: 0-10: 1, 10-20: 8, 20-30: 6, 30-40: 7, 40-50: 21, 50-60: 23, 60-70: 19, 70-80: 6, 80-90: 5, 90-100: 4. Now we see at once that most students scored between 40 and 70.
Don't confuse with
- Frequency array: this is used for a discrete variable. It is counted value by value (for example, households of size 1, 2, 3 …), not in class intervals.
Related concepts
- Raw data
- Classification
- Chronological classification
- Spatial classification
- Qualitative classification
- Quantitative classification
- Attribute
- Continuous variable
- Discrete variable
- Frequency