statistika/matematika/metode exponential smoothing

1. ABSTRACT
Emy Fitryani, 2010.-- PERTAMAX SALES FORECASTING USING
EXPONENTIAL SMOOTHING METHOD AT SPBUS IN MATARAM AND WEST
LOMBOK REGENCY (i – xiii; 49 pages) (Supervisors : I Gde Ekaputra
Gunartha and Mustika Hadijati)
Forecasting is an estimate of something that has not happened. The purpose of this
study was to determine the sales model of Pertamax at the gas stations (SPBUs) in
Mataram and West Lombok Regency using Exponential Smoothing Methods, and
then to predict the number of sales Pertamax in the next period. Exponential
smoothing method is one method of time series that provides weighting decreases
exponentially to the value of previous observations. Fitting the models in the study
carried out on weekly sales data Pertamax on period of September 2009 to May
2010 from SPBU Kekalik (Mataram), SPBU Kediri and SPBU Selagalas (West
Lombok); while validation on the forecasts of the selected models using sales data in
June 2010. Model fitting step begins with: (a). identifying the model against data
held, by making plots Pertamax sales from week to week, (b). diagnostic the model,
through determining the pattern of error variances (MSD, MAD, and MAPE) by
varying the values of  and  parameters, and optimizing  and  parameters by
minimizing error variances using Microsoft Excel Solver, (c). making forecasts of the
selected models resulted from Solver minimization, and (d). comparing the values of
the model forecasting with actual sales of Pertamax in June 2010 using 95%
confidence interval.
According to the study, the best model to predict weekly sales in the third SPBUs of
Pertamax is Double Exponential Smoothing Method (Holt). The good model for the
SPBU Kekalik was obtained by using the value of  = 0.45 and  = 0.01, with the
value of MAPE = 19, MAD = 1417 and MSD = 3320908. The SPBU Kediri was
modeled well by using  = 0.30 and  = 0.10, resulting MAPE = 11.4, MAD =
120.2 and MSD = 20631.9; while the SPBU Selagalas was suitable fitted by using 
= 0,30 and  = 0.04 and producing MAPE = 25, MAD = 940, and MSD = 1627429.
The results showed that the actual sales data Pertamax of June 2010 in the three
SPBUs are scattered within 95% confidence interval lines of the forecast model
selected. This means that the forecasts of the selected models are in accordance with
the pattern of actual data scatters. The best forecasting model obtained at the SPBU
Selagalas, followed by consecutive SPBUs of Kekalik and Kediri.
Key words : forecasting, optimization of  and  parameters, and double
exponential smoothing method
©
Program Studi Matematika – FMIPA Universitas Mataram (2010)