The total sum of squares (TSS) is calculated by adding the explained sum of squares and the residual sum of squares. From the table:

• Explained sum of squares = 825
• Residual sum of squares = 625

TSS = Explained SS + Residual SS = 825 + 625 = 1450

This is a fundamental concept in regression analysis where the total variation in the dependent variable is partitioned into explained variation (by the model) and unexplained variation (residual).