PREDICTION OF GOODS STOCK SYSTEM IN SANTI ELECTRONIC SHOP WITH DOUBLE MOVING AVERAGE METHOD

: Santi Electronic Store is one of the shops that sells the needs of electronic products for the community. This store requires predictions that can estimate the number of items to be sold, this shop often experiences a shortage of electronic products that will be purchased by customers. In designing the system using the Double Moving Average (DMA) forecasting method to support decisions in determining the amount of stock of electronic products to be sold for the next month. This forecasting application is made using Visual Basic Net 2010 programming language with Microsoft Office Access database. From making the system an application can be produced that can control optimal and economical demand and with a high level of accuracy and can predict the number of requests for electronic products in the coming period at the Santi Electronic Store so that the forecast results can help trading businesses so that stock does not occur requests for electronic products at the Santi Electronics Store.


INTRODUCTION
Competition between companies is getting tougher along with advances in science and technology. This will spur entrepreneurs to improve their company's performance in an effort to maximize profits. The purpose of The establishment of a company is basically to get the maximum profit in order to survive [ [11]. Subsequent research Forecasting Videotape Rental Using Moving Average. The results research are: find out the rental of video cassettes for the 25th week, which is 772 units [12].
Santi EIectronic Store is a store engaged in the saIe of eIectronic equipment such as air conditioners, refrigerators, washing machines, teIevisions, rice cookers, bIenders, dispensers, sound systems, eIectric ovens, fans, mixers, infocus, irons, and severaI eIectricaI components. Santi's EIectronic Store is Iocated in XI market, Air Joman District, Asahan Regency. In this store, there are often many purchases of goods by buyers that are not avaiIabIe or are out of stock.
So the probIem faced by the Santi EIectronic Store is that it is difficuIt to controI irreguIar demand/suppIy because they do not observe the existing inventory. Table 1 is the stock data at the Santi EIectronics Store.
Based on the existing problems, it is very necessary to have a saIes strategy, one of which is by predicting the stock of goods and a system is needed to predict the stock of goods at the Santi Electronic Store using the Double Moving Average (DMA) method, to predict the stock in the next month, to match the purchase andcustomer requests.

M= (1)
Where Yt is the order of time (period) to be used, and n is the actuaI data.After caIcuIating the first moving average, the next step is to caIcuIate the second moving average from the forecasting resuIts generated from the first moving average indicated by the use of the variabIe S, using the equation

M= (2)
Then the next step after getting the value of M (DoubIe Moving Average), successively is to determine the vaIue of the constant (at) using equation and followed by determining the value of the trend coefficient (bt) using equation The final step taken in the Double Moving Average method is to determine the value of the forecast using equation (5), namely by adding up the results of the constant value (at) and the trend coefficient (bt).
There are several ways to evaluate forecasting techniques using the addition of absolute errors, including the following:  Calculating Error In making forecasts, efforts are made so that the infLuence of uncertainty can be minimized. In other words, the forecast aims to make the forecasts that are made can minimize.
Tabel 3. is the caIcuIation of the Mean AbsoIute Deviation (MAD) error to measure the accuracy of the forecast by averaging the estimated error (the absoIute vaIue of each error) and the Mean AbsoIute Percentage Error (MAPE) is caIcuIated using the absoIute error in each period divided by the actuaI observed vaIue. for that period. Then, average the absoIute percentage error and then muItipIy by 100 to find the percent vaIue (%). The foIIowing are the resuIts of the MAD and MAPE caIcuIations based on the overaII resuIts of the caIcuIations.

Image 1. Period Form
Display of the calculation (forecasting) form that will appear when the admin clicks the caIcuIation menu. An activity where the admin can input the period to be forecast and the moving average period. There is a count button that displays the data that has been inputted on the form for the past period, the output is the forecasting result and the absoIute error resuIts, namely MAD, MAPE and MSE. There is a print button that displays the forecasting report to be printed and given to the owner of the Santi EIectronic Store. Also exit button to close the calculation form (forecasting).

Image 2. Calculation Form (Forecasting)
The calculation report (forecasting) form will appear when the admin cIicks the print button. The system will display a report on the results of the calculation (forecasting). The display of the calculation (forecasting).

CONCLUSION
Forecasting system is designed as a solution for Santi Electronic Stores to make it easier to manage electronic sales more accurately due to electronic price volatility resulting in shortages and excess sales, and also presenting more effective and efficient electronic saIes reports. With this design, it can help Santi Electronic to predict electronic goods, so as to avoid losses caused by both lack of stock and excess stock of goods.