There is a grouped data distribution for which mean is to be found by step deviation method. For this purpose, the below table is constructed. Fill in the blanks
Class IntervalNumber of Frequency(fi)Class mark(xi)di=xi−aui=dih0−1004050−200D......100−20039150B.....E.....200−3003425000300−400303501001400−50045450C.....F......TotalA.∑fi=......
The A, B, C, D, E and F respectively are
188 , -100, 200, -2 ,-1 and 2
∑fi= sum of frequencies of each class = 40 + 39 + 34 + 30 + 45 = 188
di = xi - a
where xi = ith class mark
a = assumed mean
Using above formula for 1st class(0-100) we get-
-200 = 50 – a
a = 250
Using above formula for 2nd class(100-200) we get-
B = 150 – 250
B = -100
Similarly, C = 200.
ui = (di)h
Here h = class interval = 100. h is constant.
For 1st class(0-100),
u1 = d1h= -200/100 = -2
Thus, D = -2
Similarly E = -1, F = 2
Answers are 188 , -100, 200, -2 ,-1 and 2