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This research aims to evaluate the effectiveness of linear regression as a forecasting tool to estimate the Provincial Minimum Wage (UMP) in Indonesia. Utilizing UMP data from various provinces during the period 2002-2022, this study employs linear regression to analyze the factors influencing UMP determination. The predicted UMP for North Sumatra in 2023 demonstrates a high level of accuracy (R-squared = 0.9678), affirming the potential of linear regression as an effective tool to understand regional economic dynamics. The research provides a crucial foundation for policymakers in regional economic planning and suggests avenues for further investigation, including exploring alternative prediction methods and analyzing the impact of UMP regulation policies.

Mitsubishi Chemical Indonesia is a producer of Purify Terepthalic Acid (PTA) in Indonesia with an important role in meeting the primary needs of the Indonesian population by managing raw materials to produce purified terepthalic acid. Purified terepthalic acid is the main raw material for polyester fiber. The problem that occurs is the phenomenon of the bullwhip effect, namely the occurrence of fluctuations between orders and demand which results in a shortage of raw materials or low inventory which can cause production to stop. So the purpose of this study is to calculate the value of the bullwhip effect, determine the causes of the bullwhip effect, and determine solutions to reduce the bullwhip effect. This study begins by calculating the value of the bullwhip effect at the two echelons. The method used in this research is FMEA. The results of this study are the value of the bullwhip effect at echelon 1 (suppliers and PPIC) = 1.27 and echelon 2 (PPIC and distributors) = 0.93. This value indicates the occurrence of a bullwhip effect in echelon 1 while echelon 2 does not indicate the occurrence of a bullwhip effect. The dominant causes of the bullwhip effect are market competition, rising material prices, demand forecasting that is not close to accurate and the number of orders for raw materials in large quantities. The proposed improvement is to collaborate with suppliers and customers to get guaranteed orders and demand that are fixed and sustainable. This value indicates the occurrence of a bullwhip effect in echelon 1 while echelon 2 does not indicate the occurrence of a bullwhip effect. The dominant causes of the bullwhip effect are market competition, rising material prices, demand forecasting that is not close to accurate and the number of orders for raw materials in large quantities. The proposed improvement is to collaborate with suppliers and customers to get guaranteed orders and demand that are fixed and sustainable. This value indicates the occurrence of a bullwhip effect in echelon 1 while echelon 2 does not indicate the occurrence of a bullwhip effect. The dominant causes of the bullwhip effect are market competition, rising material prices, demand forecasting that is not close to accurate and the number of orders for raw materials in large quantities. The proposed improvement is to collaborate with suppliers and customers to get guaranteed orders and demand that are fixed and sustainable.      

Kruskal's algorithm in searching for minimum spanning trees can be applied to pipelines installed at the location of PDAM Tirtanadi Tuasan where problem identification starts with the water discharge reaching the consumer is small but the discharge flowing from the reservoir is sufficient, so this research is used as a solution to this problem and also as an optimization of the clean water distribution network in the Tirtanadi Regional Drinking Water Company (PDAM) of the Tuasan Branch with the intention of cutting the direction of the pipe flow to overcome this problem. The data obtained from PDAM Tirtanadi Tuasan Branch is in the form of a floor plan and formed into a weighted graph. After the data is obtained, then it is calculated manually that the length of the installed water pipe is 32,645 m with 86 vertices and 100 edges, then the pipe length is represented as a set of paths and the pipe connection ends are represented as nodes. The pipe length obtained using Kruskal's algorithm and inspection of iterations using the QM for windows software is 22,095 m, with 86 vertices and 85 edges. So, using the Kruskal Algorithm and the help of the QM for windows software, the difference in pipe length obtained is 10,610 m.

Electrical energy is one of the most important things in human life. Electrical energy is needed in the industrial sector. In meeting the needs of electrical energy, good planning is needed by predicting the needs of electrical energy. Holt's Double Exponential Smoothing method is a method that can be used to predict electrical energy needs. The results of forecasting the demand for electrical energy at PT PLN (Persero) for the North Sumatra Region for 2022 to 2030 use the Double Double Exponential Smoothing method from Holt (with a value of α = 0.99 and γ = 0.1 which has a MAPE value of 2.0372%. ) namely 13933.19 gwh, 14478.46 gwh, 15023.73 gwh, 15569.00 gwh, 16114.26 gwh, 16659.53 gwh, 17204.80 gwh, 17750.06 gwh, 18295.33 gwh.

Perum Bulog as a State-Owned Enterprise has the main task, which is to conduct a quality and adequate basic food logistics business for the survival of the people. The problem that occurred in Perum Bulog Sub Divre Medan is that the rice supply in Bulog does not consider the demand in the market. Forecasting is an important tool in effective and efficient planning. Therefore, prediction is indispensable for predicting future events. This method essentially uses past data initiated by performing an exponentially decreasing weighting of older observational values or newer values. Brown's double exponential smoothing is a linear model proposed by Brown. This double exponential smoothing method is used when the data indicate a trend. In this study, the terbaik best parameter for forecasting the Number of Rice Sales in Perum Bulog Sub Divre Medan was α = 0.2 with MAPE of 0.27%. And the results of the forecast for Rice Sales at Perum Bulog Sub Divre Medan in 2022 are decreasing every month.