The following data give the number of boys of a particular age in a class of 40 students.

Age (in years) 15 16 17 18 19 20

Frequency (f_i) 3 8 9 11 6 3

Calculate the mean age of the students.

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Solution

We will make the following table:

Age (x_i) Frequency (f_i) (f_i)(x_i)

15 3 45

16 8 128

17 9 153

18 11 198

19 6 114

20 3 60

$\sum_{}^{} f_{i} =$ 40 $\sum f_{i} x_{i} =$ 698

Thus, we have:
$Mean = \frac{{\sum f_{i} x_{i}}_{}^{}}{\sum_{}^{} x_{i}}$
$= \frac{698}{40} = 17.45 years$

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Q. The following data give the number of boys of a particular age in a class of

40

students. Calculate the mean age of the students.

Age(in years)	$13$	$14$	$15$	$16$	$17$	$18$
Number of students	$3$	$8$	$9$	$11$	$6$	$3$

Q. From the following data, relating to playing habits in various age group of 900 students. Calculate coefficient of correlation between age group and playing habits.

Age Group	15−16	16−17	17−18	18−19	19−20	20−21
Number of Students	250	200	150	120	100	80
Regular Players	200	150	90	48	30	12

Q. The frequency table of the ages of 40 students in a class is given below. Find their mean age.

Age of students (in years)	11	12	13	14
Frequency	16	10	12	2

The age wise participation of students in the Annual Function of a school is shown in the following distribution.
$\begin{matrix} Age (in years) & 5 - 7 & 7 - 9 & 9 - 11 & 11 - 13 & 13 - 15 & 15 - 17 & 17 - 19 Number of students & x & 15 & 18 & 30 & 50 & 48 & x \end{matrix}$

Find the missing frequencies when the sum of frequencies is 181. Also, find the mode of the data.

The ages of 37 students in a class are given in the following table:

Find the Median

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Age (x_i)	Frequency (f_i)	(f_i)(x_i)
15	3	45
16	8	128
17	9	153
18	11	198
19	6	114
20	3	60
	$\sum_{}^{} f_{i} =$ 40	$\sum f_{i} x_{i} =$ 698

The following data give the number of boys of a particular age in a class of 40 students. Age (in years) 15 16 17 18 19 20 Frequency (fi) 3 8 9 11 6 3 Calculate the mean age of the students.

We will make the following table: Age (xi) Frequency (fi) (fi)(xi) 15 3 45 16 8 128 17 9 153 18 11 198 19 6 114 20 3 60 ∑fi = 40 ∑fixi=698 Thus, we have: Mean = ∑fixi∑xi = 69840= 17.45 years

The following data give the number of boys of a particular age in a class of 40 students.

Age (in years) 15 16 17 18 19 20

Frequency (f_i) 3 8 9 11 6 3

Calculate the mean age of the students.

We will make the following table:

Age (x_i) Frequency (f_i) (f_i)(x_i)

15 3 45

16 8 128

17 9 153

18 11 198

19 6 114

20 3 60

$\sum_{}^{} f_{i} =$ 40 $\sum f_{i} x_{i} =$ 698

Thus, we have:
$Mean = \frac{{\sum f_{i} x_{i}}_{}^{}}{\sum_{}^{} x_{i}}$
$= \frac{698}{40} = 17.45 years$