If , then =

We have given,

Also,

Putting this in above equation

Now, given …[1]

using this

We have,

…[2]

We know,

If x₁, x₂, … , x_n are observations with frequencies f₁, f₂, … , f_n i.e. x₁ occurs f₁ times and x₂ occurs f₂ times and so on, then mean() of observations is given by

From [1] and [2]