It implies the summation of the values. Sf i N Total number of observations. Arithmetic Mean xi n.
In direct method the arithmetic mean is calculated by the following formula.
If there are n classes and f i denotes the frequency and y i denotes the class-mark of the i th class the mean is given by Mean Sf i y i Sf i When the number of classes is large or the value of f i and y i is large an approximate assumed mean is taken near the middle represented by A and deviation d i is taken into consideration. In the above Equation the symbol is known as sigma. Here x₁ x₂ x₃ etc. The formula for the arithmetic mean is.
