Question

The following table shows the quarterly demand in thousands of cases, for a national beer distributor over the past four years. This data is also available in an Excel spreadsheet on Blackboard.

	Year
Quarter	2015	2016	2017	2018
1	280	321	419	266
2	485	493	502	510
3	423	515	487	501
4	330	271	468	516

1.                                                                                         Using a smoothing coefficient of a = 0.3, exponentially smooth the series. Assume an initial forecast for the first quarter of 2015 of 300. Show:

- the MAD and MAPE

- a plot of the actuals and forecast on a properly labeled chart.

- the forecast for the first quarter of 2019.

Answer 1

The calculations are:

Year	Quarter	Data	Forecast	Error	Absolute Error	Squared Error	MAPE
2015	1	280
	2	485	300	185	185	34225	38.14433
	3	423	355.5	67.5	67.5	4556.25	15.95745
	4	330	375.75	-45.75	45.75	2093.063	13.86364
2016	1	321	362.025	-41.025	41.025	1683.051	12.78037
	2	493	349.7175	143.2825	143.2825	20529.87	29.06339
	3	515	392.7023	122.2978	122.2978	14956.74	23.74714
	4	271	429.3916	-158.392	158.3916	25087.89	58.44708
2017	1	419	381.8741	37.1259	37.1259	1378.332	8.860596
	2	502	393.0119	108.9881	108.9881	11878.41	21.71078
	3	487	425.7083	61.29169	61.29169	3756.671	12.58556
	4	468	444.0958	23.90418	23.90418	571.41	5.107731
2018	1	266	451.2671	-185.267	185.2671	34323.89	69.64928
	2	510	395.687	114.313	114.313	13067.47	22.41432
	3	501	429.9809	71.01913	71.01913	5043.717	14.17548
	4	516	451.2866	64.71339	64.71339	4187.823	12.54136
2019	1		470.7006	MAD	95.32462	MAPE	23.93657

The plot is: