8. The table given below shows the age distribution of 1000 persons who
visited a marketing centre on a Sunday.
Age in years) 0-10
10-20 20-30 | 30-40 40-50 50-60 60-70
Number of
105 222 220 138
113
100
persons
Find the mean age of the persons visiting the marketing centre on
that day.
(CBSE 2015)
HINT Use step deviation method taking A = 35 and h = 10.
102
Answers
Answer:
A=35 and h=10
C.I Classmark
x
i
d
i
=x
i
−A u
i
=
h
d
i
f
i
f
i
u
i
0−10 5 −30 −3 105 −315
10−20 15 −20 −2 222 −444
20−30 25 −10 −1 220 −220
30−40 35 0 0 138 0
40−50 45 10 1 102 102
50−60 55 20 2 113 226
60−70 65 30 3 100 300
∑f
i
=1000 ∑f
i
u
i
=−351
⇒ Required mean =A+
∑f
i
∑f
i
u
i
×h
=35+
1000
(−351)
×10
=35−3.51
=31.49
Answer:
Step-by-step exp⇒
Required mean
=
A
+
∑
f
i
u
i
∑
f
i
×
h
=
35
+
(
−
351
)
1000
×
10
=
35
−
3.51
=
31.49lanation: