In a retail market, fruit vendors were selling mangoes kept in packing boxes. These boxes contained varying number of mangoes. The following was the distribution of mangoes according to the number of boxes.

It can be observed that class intervals are not continuous. There is a gap of 1 between two class intervals. Therefore, 1/2 [0.5) has to be added to the upper-class limit and 1/2 (0.5) has to be subtracted from the lower-class limit of each interval. Class mark (xᵢ) can be obtained by using the following relation.
xᵢ = (Upper Limit + Lower Limit)/2
Class size (h) of this data = 3. Taking 57 as assumed mean (a), dᵢ, uᵢ, fᵢuᵢ are calculated as follows.

It can be observed that
∑fᵢ = 400, ∑fᵢuᵢ = 25, a = 57 and h = 3
mean (X̄) = a + (∑fᵢuᵢ / ∑fᵢ)h = 57 + (25/400) × 3 = 57 + 3/16 = 57 + 0.1875 = 57.19
Mean number of mangoes kept in a packing box is 57.19.
Set deviation method is used here as the values of fᵢdᵢ are big and also, there is a common multiple between all dᵢ.