Statistics — Part 1: Mean of grouped data: visual lesson, CBSE Class 10 Mathematics (Standard 041 / Basic 241)

Lesson

Statistics, Part 1: Mean of grouped data

Forty batters, five classes of runs: what is the average score?

In this lesson you will

Runs scored by 40 batters in a district tournament.

Concept

Diagram

Class mark $=$ (lower $+$ upper) $\div 2$.
Class	Lower limit	Upper limit	Class mark $x_i$
0–20	$0$	$20$	$10$
20–40	$20$	$40$	$30$
40–60	$40$	$60$	$50$
60–80	$60$	$80$	$70$
80–100	$80$	$100$	$90$

In grouped data we do not know the individual values. We assume every value in a class sits at its mid-point, the class mark:

x_i = \frac{\text{lower limit} + \text{upper limit}}{2}