Statistics

Mean is the sum of all

Mean is the sum of all observations divided by the total number of observations. For grouped data, class marks are used as representative values. Mean

Class mark is the midpoint

Class mark is the midpoint of a class interval. It is found by adding the lower and upper class limits and dividing by 2. It acts as the representativ

In the direct method

In the direct method, mean is found using \(\bar{x} = (\sum f_i x_i)/(\sum f_i)\), where \(x_i\) are class marks and \(f_i\) are frequencies.

A convenient class mark is chosen

A convenient class mark is chosen as assumed mean \(a\). Deviations are calculated by \(d_i = x_i - a\), and mean is found using \(\bar{x} = a + (\sum

This method uses \(u_i = (x_i

This method uses \(u_i = (x_i - a)/h\), where \(h\) is the class size or a suitable divisor. Mean is found using \(\bar{x} = a + ((\sum f_i u_i)/(\sum