Root Mean Square Deviation (RMSD) quantifies the discrepancy between a model's predictions and actual observed values. It is computed as the square root of the mean of the squared differences between predicted and actual values. The formula is RMSD = $\sqrt{\frac{\sum{(Predicted - Actual)^2}}{n}}$, where 'n' represents the total number of observations. RMSD serves as a common metric in data analysis for evaluating predictive model accuracy. A smaller RMSD signifies that the model's predictions are more aligned with the actual values, indicating superior performance. This metric aids analysts in model comparison and selection based on the lowest prediction error.