Question

Calculate the mean of the following table:

Interval	fi
0-10	6
10-20	5
20-30	7
30-40	8
40-50	3

• A. 25.7
• B. 27.7
• C. 23.9
• D. 21.4

Answer 1

Answer:

C. 23.9

Solution:

Concept used: 

Mean = $\dfrac{Σ f_ix_i}{Σ f_i}$

$x =\dfrac{UpperLimit + LowerLimit}{2}$

Calculation:

Interval	fi	xi	Σfixi
0 - 10	6	5	30
10 - 20	5	15	75
20 - 30	7	25	175
30 - 40	8	35	280
40 - 50	3	45	135

 

Σf_i = 6 + 5 + 7 + 8 + 3 = 29

⇒ Σf_ix_i = 30 + 75 + 175 + 280 + 135 = 695

Mean = $\dfrac{Σ f_ix_i}{Σ f_i}$ = $\frac{695}{29}$ = 23.9

∴ The mean is 23.9