Find variance for following data:
Class interval $30 - 40$ $40 - 50$ $50 - 60$ $60 - 70$ $70 - 80$ $80 - 90$ $90 - 100$
Frequency $3$ $7$ $12$ $15$ $8$ $3$ $2$

14.17

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18.17

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16.17

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15.17

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Solution

The correct option is A $14.17$
$¯ x = \frac{\sum F x}{\sum F} = \frac{3100}{50} = 62$
$σ^{2} = \frac{\sum F (x - ¯ x)^{2}}{\sum F} = \frac{10050}{50} = 201$
$σ = 14.17$

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Similar questions

Class interval	$30 - 40$	$40 - 50$	$50 - 60$	$60 - 70$	$70 - 80$	$80 - 90$	$90 - 100$
Frequency	$3$	$7$	$12$	$15$	$8$	$3$	$2$

Class	$0 - 10$	$10 - 20$	$20 - 30$	$30 - 40$	$40 - 50$	$50 - 60$	$60 - 70$
frequency	$6$	$5$	$8$	$15$	$7$	$6$	$3$

Class interval	$10 - 20$	$20 - 30$	$30 - 40$	$40 - 50$	$50 - 60$	$60 - 70$	$70 - 80$	$80 - 90$
Frequency	$4$	$6$	$8$	$10$	$12$	$14$	$7$	$5$

Class interval	$10 - 20$	$20 - 30$	$30 - 40$	$40 - 50$	$50 - 60$	$60 - 70$	$70 - 80$	$80 - 90$
Frequency	$4$	$6$	$8$	$10$	$12$	$14$	$7$	$5$

80, 10, 30, 70, 60, 50, 50, 40, 40, 20, 40, 90, 50, 30, 70, 10, 60, 50, 20, 70, 70, 30, 80, 40, 20, 80, 90,

50, 80, 60, 70, 40, 50, 60, 90, 60, 40, 40, 60

60

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