If mean is166 9/26(mixed fraction) andsum of observations is 52.Findf1 and f2.
C I FREQUENCY
140 - 150 5
150 -160 f1
160 -170 20
170-180 f2
180-190 6
190-200 2
Let assumed mean be A = 175 , h = 155-145 = 10
C I FREQUENCY MID VALUES(x) d = x-A u=(x-A)/h fu
140 - 150 5 145 -30 -3 -15
150 -160 f1 155 -20 -2 -2f1
160 -170 20 165 -10 -1 -20
170-180 f2 175 0 0 0
180-190 6 185 10 1 6
190-20 2 195 20 2 4
= -25-2f1
sum of frequency = 33+f1+f2
given sum of frequency = 52
hence , 33+f1+f2 = 52
f1+f2 = 52-33
f1+f2 = 19 …………….(1)
we know
mean = A + h
= 175 + 10*
= 175 +
=
4325*2 = 8850-20f1
8650 – 8850 = -20f1
F1 = 200/20
= 10
Now we have f1+f2 = 19
10 + f2 = 19
f2 = 19-10
= 9 ans