The mean heights of three groups of students consisting of 20, 16 and 14 students each are 1.67m, 1.50m and 1.40m respectively. Find the mean height of all the students.
- 1.63m
-
1.54m
- 1.52m
- 1.42m
The correct answer is: B
Explanation
for 20 students, mean = 1.67
| μ | = | ∑fx
f |
∑fx = μf
∑fx = 20 × 1.67 = 33.4
for group 2
∑fx = 16 × 1.50 = 24
for group 3
∑fx = 14 × 1.40 = 19.6
33.4 + 24 + 19.6 = 77
∑f = 20+16+14 = 50
| μ | = | 77
50 |
= | 1.54m |