Find the arithmetic mean of the following frequency distribution:
Class Interval $0 - 20$ $20 - 40$ $40 - 60$ $60 - 80$ $80 - 100$ $100 - 120$ $120 - 140$
Frequency $12$ $18$ $15$ $25$ $26$ $15$ $9$

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Solution

Make the required frequency distribution table.
Class Interval $x_{i}$ Frequency, $f_{i}$ $x_{i} f_{i}$
$0 - 20$ $10$ $12$ $120$
$20 - 40$ $30$ $18$ $540$
$40 - 60$ $50$ $15$ $750$
$60 - 80$ $70$ $25$ $1750$
$80 - 100$ $90$ $26$ $2340$
$100 - 120$ $110$ $15$ $1650$
$120 - 140$ $130$ $9$ $1170$
Total $\sum_{}^{} f_{i} = 120$ $\sum_{}^{} f_{i} x_{i} = 8320$
Calculate the Mean.
Mean $= \frac{\sum_{} f_{i} x_{i}}{\sum_{} f_{i}}$
$X = \frac{8320}{120}$
$\bar{X} = 69.33$
Hence, the mean for the given distribution data is $\bar{X} = 69.33$ _.

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Similar questions

Class	0-20	20-40	40-60	60-80	80-100	100-120	120-140
Frequency	12	18	15	25	26	15	9

Classes:	$0 - 20$	$20 - 40$	$40 - 60$	$60 - 80$	$80 - 100$	$100 - 120$	$120 - 140$
Frequency:	$6$	$8$	$10$	$12$	$6$	$5$	$3$

Calculate the arithmetic mean of the following frequency distribution:

Class-interval	$0 - 20$	$20 - 40$	$40 - 60$	$60 - 80$	$80 - 100$	$100 - 120$	$120 - 140$
Frequency	$12$	$18$	$15$	$25$	$26$	$15$	$9$

Find the mean for each of the following frequency distribution

Class interval

Frequency

$0 - 20$

$20 - 40$

$40 - 60$

$60 - 80$

$80 - 100$

$100 - 120$

$120 - 140$

$12$

$18$

$15$

$5$

$26$

$15$

$9$

Class interval	$0 - 20$	$20 - 40$	$40 - 60$	$60 - 80$	$80 - 100$	$100 - 120$	$120 - 140$
Frequency	$4$	$15$	$23$	$12$	$16$	$8$	$2$

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