Measuring Forecast Accuracy in a Pharmacy

Results and Discussion

Sales Forecast using 2-Month Moving Average Method

The study used 2-month moving average method to be able to even out the peak and valley in the sales figures for two months which tends to generate better forecast as indicated in table 2. Also, the accuracy of the forecasting method was evaluated as represented in table 2.

Table 2. Actual and Forecasts using 2-Month Moving Average Method

Month (x)	Actual sales (y) (million)	Forecast	IEI	IEI²	E/Y x100
1	25	-	-	-
2	29	-	-	-
3	28	24.5	3.5	12.25	12.5
4	35	28.5	6.5	42.25	18.57
5	33	31.5	1.5	2.25	4.55
6	32	34	2	4	6.25
7	36	32.5	3.5	12.25	9.72
8	41	34	7	49	17.07
9	45	38.5	6.5	42.25	14.44
10	20	43	23	529	115
11	23	32.5	9.5	90.25	41.30
12	15	21.5	6.5	12.25	43.33

The forecast accuracy performance measures are:

\(\mathrm{MAD}=\Sigma / \mathrm{E} / / \mathrm{T}=69.5 / 12=5.79, \mathrm{MSE}=\Sigma / \mathrm{E} /{ }^{2} \mathrm{~T}=795.75 / 12=66.31\)

MAPE = (Absolute error / Actual Observed Value) × 1 00 = 282.73/12= 23.56.