For a sample of n subjects the relative frequencies are f0n

Question

For a sample of n subjects, the relative frequencies are f₀/n = .2, f₁/n = .4, f₂/n = .2, f₃/n = .15, and f₄/n = .05. The sample mean is 1.45. Using your answer to given Exercise, verify that the sample variance is 1.25.

Exercise

Referring to the description of the population variance, σ², devise a method of estimating σ² based on the frequencies, f_x.