Statistics (Grouped Data)

Introduction

In earlier classes, you learned mean, median, and mode for ungrouped (individual) data. In Class 10, we extend these concepts to grouped data — data organized into class intervals. This is how real-world data is usually presented: marks in ranges, income brackets, age groups, etc.

Key Terms

Class interval: A range like 10-20, 20-30 (continuous) where 10-20 means 10 ≤ x < 20.
Class mark (xᵢ): Midpoint of a class = (lower limit + upper limit)/2. Example: class mark of 10-20 = 15.
Frequency (fᵢ): Number of observations in a class.
Cumulative frequency (cf): Running total of frequencies from top.
Class width (h): Upper limit – lower limit. Example: for 10-20, h = 10.