The given formula is known as ___________.

$\left(\overline{\mathrm{x}}\right) = \mathrm{a} + \frac{\underset{ }{\sum {\mathrm{f}}_{\mathrm{i}}{\mathrm{d}}_{\mathrm{i}}}}{\sum _{ }{\mathrm{f}}_{\mathrm{i}}}$

The step deviation approach is an extension of the shortcut or assumed method for calculating the mean of big variables. 

These deviation values can be divided by a common factor with a smaller value. The scale method or change of origin are other names for the step deviation method.

So, according to the assumed mean method : $\left(\overline{\mathrm{x}}\right) = \mathrm{a} + \frac{\underset{ }{\sum {\mathrm{f}}_{\mathrm{i}}{\mathrm{d}}_{\mathrm{i}}}}{\sum _{ }{\mathrm{f}}_{\mathrm{i}}}$