| | | | | | |
| | | | | | |
Class interval
Frequency
50 – 70
18
70 – 90
12
90 – 110
13
110 – 130
27
130 – 150
8
150 – 170
22
(4 marks)
Find the mean of each of the following frequency distributions (5 – 14)
6
Sol.
Class interval
Class
Mark (xi)
di =
fiui
60
Total
--
--
Σ fiui =
61
Class width(h)
= 20
– 20
0
20
40
– 40
– 1
0
1
2
– 2
60 + 20
100
120
140
80 + 20
100 + 20
120 + 20
= xi –
100
100
Assumed Mean (A) =
100
60 - 100
80 - 100
100 – 100
120 - 100
140 - 100
80
No. of workers (fi)
Σ fi =
100
--
ui=
di
g
=
di
20
×
×
×
×
×
+
+
+
+
+
+
+
+
12
13
27
8
18
0
50 - 70
70 - 90
90 - 110
110 - 130
130 - 150
A
50 + 70
2
40
20
20
20
0
20
20
– 40
–20
– 48
109
– 36
– 12
27
16
20
xi
– A
Mean
=
Σ fi
Σ fiui
60
3
160
140 + 20
160 - 100
+
+
22
150 - 170
66
60
20
×
g is the G.C.D. of all values of di
| | | | | | |
| | | | | | |
Class interval
Frequency
50 – 70
18
70 – 90
12
90 – 110
13
110 – 130
27
130 – 150
8
150 – 170
22
(4 marks)
Find the mean of each of the following frequency distributions (5 – 14)
6
Sol.
u
=
Σ fiui
Σ fi
=
61
100
=
u
Σ fiui =
61
Σ fi =
100
∴
0.61
=
A
+
u
×
g
=
100
+
20
=
100
=
112.2
+
12.2
(0.61)
∴
Assumed Mean (A) =
100
G.C.D of all di (g)
= 20