Formulae [1]
Formula: Mean of Grouped (Tabulated) Data
Direct Method:
\[\bar{x}=\frac{\sum f_ix_i}{\sum f_i}\]
where xi = class mark, fi = frequency
Short-cut (Assumed Mean) Method:
\[\bar{x} = A+\frac{\sum f_id_i}{\sum f_i}\]
where di = xi - A
A is the assumed mean
Step-deviation Method:
\[\bar{x}=a+h\frac{\sum f_iu_i}{\sum f_i}\]
where \[u_i=\frac{x_i-a}{h}\]
h is the class width / common factor
