Age 3 4 5 6 7 8 9 10 No. of children 2 6 5 4 6 9 8 5 The table shows the distribution of ages of a number of children in a school. If the mean of the distri...

Question 1 Report

Age	3	4	5	6	7	8	9	10
No. of children	2	6	5	4	6	9	8	5

The table shows the distribution of ages of a number of children in a school. If the mean of the distribution is 7, find the;

(a) value of x, (b) standard deviation of their ages.

Answer

Mean = (3x2 +4x6 + 5x5 + 6x + 7x6 + 8x9 + 9x8 + 10x5) ÷ (2 + 6 + 5 + x + 6 + 9 + 8 + 5)

7 = (291 + 6x) ÷ (41+x)

7(41+x) = 291 + 6x

287 + 7x = 291 + 6x

x = 4

(b)

Age(x in yrs)	No.of child	Fx $^{2}$
3	2	18
4	6	96
5	5	125
6	4	144
7	6	294
8	9	576
9	8	648
10	5	500
	Σf = 45	Σfx $^{2}$ = 2401

Standard deviation = $\sqrt{\frac{196}{45}} = \sqrt{4} .3555$

= 2.087

Read lesson note on Surds (radicals) (WAEC)

Read lesson note on Statistics (WAEC)

Answer Details

Mean = (3x2 +4x6 + 5x5 + 6x + 7x6 + 8x9 + 9x8 + 10x5) ÷ (2 + 6 + 5 + x + 6 + 9 + 8 + 5)

7 = (291 + 6x) ÷ (41+x)

7(41+x) = 291 + 6x

287 + 7x = 291 + 6x

x = 4

(b)

Age(x in yrs)	No.of child	Fx $^{2}$
3	2	18
4	6	96
5	5	125
6	4	144
7	6	294
8	9	576
9	8	648
10	5	500
	Σf = 45	Σfx $^{2}$ = 2401

Standard deviation = $\sqrt{\frac{196}{45}} = \sqrt{4} .3555$

= 2.087

Read lesson note on Surds (radicals) (WAEC)

Read lesson note on Statistics (WAEC)

Surds (radicals)

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