Mean of Grouped Data

Core concept

The assumed mean method selects one class's midpoint as a reference point (assumed mean, 'A'), calculates deviations (dᵢ=xᵢ-A) from this reference for each class, then adjusts the final mean using these deviations — reducing the size of numbers involved in calculations. The step-deviation method further simplifies this by dividing each deviation by the common class width (h), useful when class intervals are all equal in width, making manual calculations considerably faster and less error-prone for larger data sets.