Find the mean of each of the following frequency distributions: (5 – 14)
| | | | | |
| | | | | |
Class interval
Frequency
0 - 8
5
8 - 16
6
16 - 24
4
24 - 32
3
32 - 40
2
(3 marks)
Sol.
Class
interval
Class Mark
(xi)
di =
fidi
4
Total
--
--
Σ fidi =
– 72
Class width
= 8
–8
0
8
16
–16
Frequency (fi)
Σ fi =
20
4 + 8
20
28
36
12 + 8
20 + 8
28 + 8
= xi –
20
Assumed Mean (A) =
20
4 - 20
12 - 20
20 - 20
28 - 20
36 - 20
×
×
×
×
×
12
+
+
+
+
6
4
3
2
5
0
0 - 8
8 - 16
16 - 24
24 - 32
32 - 40
A
0 + 8
2
– 128
56
–80
–48
24
32
xi
– A
20
+
+
+
+
Lower limit + upper limit
2
Class mark =
Q.
Σ fi
A
Mean
=
+
Σ fidi
RD – 15.23 - Level-1 – Q11
Find the mean of each of the following frequency distributions: (5 – 14)
| | | | | |
| | | | | |
Class interval
Frequency
0 - 8
5
8 - 16
6
16 - 24
4
24 - 32
3
32 - 40
2
(3 marks)
Sol.
Q.
d
=
Σ fidi
Σ fi
=
– 72
20
=
d
A
+
d
=
20
( 3.6)
=
16.4
Σ fidi =
–72
Σ fi =
20
Assumed Mean (A) =
20
1
3
=
16.4
∴
6
0
∴
+
–
Mean
– 3.6
=
20
–
3.6