There are three (3) techniques of trend projection based on time – series data.
1. Graphical Method: - under this method, annual sales data is plotted on a graph paper and a line is drawn through the plotted points. Then a free hand line is so drawn that the total distance between the line and the point is minimum. Although this method is very simple and least expensive, the projections made through this method are not very reliable. The reason is that the extension of the trend line involves subjectivity and personal bias of the analysis.
Years /Trend Projection
2. Fitting Trend Equation: Least square method: - Fitting trend equation is a formal technique of projecting the trend in demand. Under this method, a trend line (or curve) is fitted to the time – series data with the aid of statistical techniques. The form of the trend equation that can be fitted to the time series data is determined either by plotting the sales data or by trying different forms of trend equations for the best fit. * When plotted, a time series date may show various trends. The most common types of trend equation are 1) liner and
2) exponential trends
* Linear Trend: - When a time series data reveals a rising trend in sales than a straight-line trend equation of the following form is fitted. (S = A + BT ; Where S = annual sales , T = Time (in year) , A & B are constant. The parameter b given the...