Question

plz tell me how to find simple arithmetic mean by direct method ,  short-cut method and step deviation method !!!! plzz help!! I've got half yrly xams!!

Answer 1

for direct method formula= sigma fixi÷sigma fi
step deviation : sigma fiui×h÷sigma fi +a here ui=di÷a
short cut method : sigma fidi÷sigma fi+a here di=xi-a

Answer 2

Direct method
x dash (put the dash over x) = ∑x / N
where x dash :- arithmetic mean
∑x :- sum of total observation or item
N :- total no. of items 
Short-cut method
x dash = A+∑d / N
where x dash = arithmetic mean
A = assumed mean
d = x - A i.e., deviations of variables from assumed mean
∑d = sum of deviations of variables from assumed mean
N = total no. of items
Step-deviation method
x dash = (x - A) / C
where x dash = arithmetic mean
∑d = x - A i.e., deviations of variables from assumed mean
d' = (x - A) / C i.e., step deviations
∑d' = sum of step deviation
C = common factor
N = total no. of items
 and if u hav further doubts like where frm did the d' come along den inbox me !! :)