Comparison of the attribution of hours lost to influenza: assessing model fit. The actual hours lost less baseline (excess) is compared with the model predicted hours lost less baseline. The difference between the two curves are known as model residuals (and equal to actual - baseline). Residuals represent the variation not explained by the model. The influenza-attributed curve is smoother as the residuals, or unexplained variation, are not included in this time series. The residuals will average out over a season. The model fit is reasonable, though the model seems to miss the occasional dip in hours lost over the summer period.