中文摘要
採購人員的首要目標，通常是在合理的品質以及交期情況下，以合理的採購價格購入合理的部品或服務。A公司主要生產偏光板，以其為例，採購部門所需採買的範圍廣泛，大致上可分為非經常性採購(例如設備、工程、修繕…等)，以及經常性採購(例如生產所需的原物料、化學品、耗材…等)，其中，原物料的購買直接影響A公司的成本及獲利能力，是該公司極為重視的區塊。
在A公司生產偏光板所需的原物料中，本研究以其中的PET材質原物料作為研究標的物，假設品質及交期皆符合買方所需的情況下，使用最小平方法(OLS)迴歸模型來尋找除了最常被探討的價格、數量以外，是否還有其他更顯著的採購價格影響要因，使採購人員往後能夠收集這些要因的客觀資料，進而以一個具可信度的迴歸式來幫助制定下次的採購目標價格。
本研究以供需、貨幣等經濟理論作為基礎，挑選出數個影響採購價格的變數，對A公司的PET離型膜及PET保護膜進行迴歸分析，結果發現，兩個迴歸所得之模型整體配適度皆達到八成以上的信賴程度，但部分變數的表現並不顯著，且亦有某部分的變數係數符號不如預期，本研究也對於這些情況原因進行討論。
本研究認為，以A公司為例，至今為止多採用主觀判定的方式來進行採購目標價格的制定，是否有機會嘗試與以往不同方向的方式來進行採購實務的作業。以驗證的結果而言，可信度雖未達到最佳，但尚具有中上等級的顯著性，若能佐以採購主管的主觀經驗，相信可以提供給採購人員更有信心達成的價格目標，藉由客觀的數據分析，也可以判別採購人員對於目標價格的達成度。
關鍵字：偏光板、PET、最小平方法(OLS)

Extended Abstract

The setting and prediction of purchasing target price：
Using PET raw materials in A-Company as example

Student’s Name: Li-Chin Ke
Advisor’s Name: Hsin-Hong Kang
National Cheng Kung University
Department of Business Administration
SUMMARY

This study attends to discuss that how to set up a subjective purchasing price using PET raw materials in A-Company witch produces LCD polarizer as the main product as example. Polarizer is an important component of LCD monitors and composed of layers of optical functional films almost supplied form Japan. Some of the optical films are made by PET (Polyethylene Terephthalate). This study choose several variables base on economic theories and cost analysis, then using multiple regressions in ordinary least squares (OLS) to build models for predicting target prices for purchasing PET raw materials. The result shows that the verified models still remain reliability above 80~90%, and is advised to be used in A-Company.

Key words: Polarizer, PET, Ordinary least squares (OLS).

INTRUDUTION

The primary target of a purchaser is to buy in parts or services with appropriate quality and delivery under appropriate prices. In this study, the sample object, A-company, produce LCD polarizer as their main products. The purchasing range of the procurement department of A-company is wide and contains irregular purchasing such as facilities, equipments, or construction services…etc. In the other hand, besides the irregular purchasing parts, the regular purchasing includes raw materials, chemicals or other expendable things…etc. The cost of the raw materials effect the profits of A-company directly, so that purchasing raw materials is quite concerned in A-company.

Polarizer is made by layers of optical functional films and two of these layers are made from PET material: Release Film and Protective Film. This study uses OLS (Ordinary least squares) to build a regression model to predict an objective target price when purchasing PET release films and protective films assuming that all conditions of qualities and deliveries are accepted by A-company.

In this study, we find some variables base on the Law of Demand and Supply, currency effects, and cost analysis, and build two models separately for PET release films and protective films. According to the regression results, the models remain 80~90% reliabilities. Also, in this study, we give some explanations to describe the reasons that why some variables are not reliable.

MATERIALS AND METHODS

Base on the Law of Demand and Supply, currency effects, and cost analysis, this study first figured out relative variables to PET and collected 2010~2014 monthly raw data of these variables. The meaning and the purposes of these variables are also described in the study (Showed simply as table 1-1 in the next page). Then we input these variables to build two first version regression models by using OLS.

Table 1-1 List of Variables
Variable
Code Variable Type Variable Meaning
MP Dependent Var.
In release film model Monthly average price of M- release film company
TP Independent Var. Monthly average price of T- release film company
NP Dependent Var.
In protective film model Monthly average price of N- protective film company
INAP Independent Var. Monthly average price of I- protective film company
SFTN Independent Var. Monthly total release film needs of A-company
PFTN Independent Var. Monthly total protective film needs of A-company
IT Independent Var. Monthly total LCD Panel shipping amounts of X-company
SP Independent Var. Monthly average price of S- PET film company
EGP Independent Var. Monthly average price of EG
PTAP Independent Var. Monthly average price of PTA
OP Independent Var. Monthly average price of Oil
UTJ Independent Var. Monthly average currency of USA and Japan
MEGA Dummy Var. Mega event (311 Japan Earth Quake)

RESULTS AND DISCUSSION

After testing the reliability of models and delete unreliable variables, we got the final regression one by one as the table showed in the appendix of the end of the extended abstract (See the table 1-2 and 1-3 in the appendix of the end).
Although some variables’ coefficients are not as expected, but according to the results of regressions, the model for release film price predicting still has 86% reliability and the one for protective film has 96% reliability. The reasons cause these problems probably because of omits of variable biases.

CONCLUSION

The models in this study are not perfect, but we hope that the results still can be referenced or used by A-company since that they never try it before. On the other hand, because of unexpected coefficients, it means that there might be more important factors should be discussed or found. By learning more experiences or collecting more market information, this study trusts that the purchasers of A-company can find out more specific factors and fix or keep the models in the highly reliable status. And that will make them to set up their purchasing target price in more objective ways.

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