Qualitative forecasts and causal forecasts are not particularly useful as inputs to inventory and scheduling decisions because they are both estimations based on expert judgment to provide insights into future outcomes. Qualitative forecasts are less objective and precise to rely on for inventory and scheduling decisions as they lack numerical analysis. Causal factors are unplanned and unintended contributors to an incident and must precede the effect to be recognized as causal factors and therefore cannot be incorporated into inventory and scheduling decisions.

Forecastingis the process of making predictions of the future based on past and present data. This is most commonly by analysis of trends. A commonplace example might beestimationof some variable of interest at some specified future date.Predictionis a similar, but more general term. Both might refer to formal statistical methods employingtime series,cross-sectionalorlongitudinaldata, or alternatively to less formal judgmental methods. Usage can differ between areas of application: for example, inhydrology,the terms "forecast" and "forecasting" are sometimes reserved for estimates of values at certain specificfuturetimes, while the term "prediction" is used for more general estimates, such as the number of times floods will occur over a long period.

Riskanduncertaintyare central to forecasting and prediction; it is generally considered good practice to indicate the degree of uncertainty attached to specific forecasts. In any case, the data must be up to date in order for the forecast to be as accurate as possible. In some cases, the data used to predict the variable of interest is itself forecasted.