Demand Forecasting required by each company in order to gain efficiency and effectiveness. Basically, Forecasting Approaches can be classified into two approaches. Classification of forecasting methods are :
a. Qualitative Approach
Qualitative approach is subjective, where the forecasting is based on the judgment, opinions, experiences and forecasters predicted (forecaster), decision makers or experts. This approach is used when historical data are not available at all.
b. Quantitative Approach
Quantitative approaches include the method of time series (time series) and the method of causal (explanatory). Time series methods to predict the future based on past data without looking at factors that affect the data. Methods of causal factors that predicted assuming a causal relationship to several independent variables.
Quantitative approach can be applied when there are three conditions as follows :
a) Available information about the past.
b) past information may be quantitative in the form of numerical data.
c) It can be assumed that some aspects of past patterns will continue in the future.