Mathematics · important
Step-deviation method for variance for JEE
Calculation of standard deviation, variance and mean deviation for grouped and ungrouped data
Formula
\(\sigma=h\sqrt{\frac{\sum f_i u_i^2}{N}-\left(\frac{\sum f_i u_i}{N}\right)^2}\), \(u_i=\frac{x_i-a}{h}\)
Variables: \(a\): assumed mean, \(h\): common factor/class width, \(x_i\): value/class mark, \(f_i\): frequency.
Conditions: Useful when deviations are integral after scaling by \(h\).
Grouped data variance with equal class intervals.