Question

For the following distribution, calculate mean using all suitable methods:

Size of item	1-4	4-9	9-16	16-27
Frequency	$6$	$12$	$26$	$20$

Answer 1

size	x	f	xf
1-4	2.5	6	15
4-9	6.5	12	78
9-16	12.5	26	325
16-27	21.5	20	430

mean $=\frac{\sum fx}{\sum f}$

$=\frac{848}{64}=13.25$