如何精確地估算軟體功能點數以便對軟體專案進行妥善的規劃和監控，是一個非常重要的課題。以往在探討軟體功能點數精確性的文獻中，只有著重在分析功能點數平均變動的範圍，並沒有將焦點放在探討影響功能點數精確性的因素為何。另外又由於軟體功能點數的計算是依據功能點計算實務手冊內所制定的判斷規則，而這些判斷規則是採用具有模糊特性的自然語言方式來呈現，然而文獻中並未指出哪些規則容易造成判斷錯誤以及其原因為何。因此，本篇論文的主要目的是探討軟體開發方法技術、生命週期階段、與軟體功能點數計算人員之教育背景、軟體開發專業經驗、功能點教育訓練對功能點數計算之精確度的影響與易造成功能點數計算錯誤的判斷規則與其原因。
透過對台灣科技大學資訊管理系一般與在職碩士研究生進行軟體系統功能點數計算個案探討與半結構式訪談，從41份有效回收樣本與7位訪談資料的分析結果發現：功能點分析方法的教育訓練對功能點數計算的精確度有顯著的影響效果，而軟體開發方法技術、生命週期階段、與軟體功能點數計算人員之教育背景、軟體開發專業經驗對功能點數計算的精確度則並無顯著的影響效果。另本研究亦彙整出易造成功能點計算判斷錯誤的規則、類型與其原因，並據以提出輔助規則判斷的使用指引。綜合上述的研究發現，我們認為影響軟體功能點數計算精確度的關鍵因素主要是在於軟體功能性需求規格的完整性、軟體功能點數計算人員對該軟體系統領域知識的熟悉度與對功能點數判斷規則的瞭解程度。因此，在計算軟體功能性大小時，必須加強計算人員對軟體功能點分析方法的專業能力與對該軟體系統領域知識的瞭解，並輔以較口語化之判斷規則、使用指引與實例說明，才能提昇功能點數計算的正確性。

How to precisely count software function points is a key to developing the software project planning and accordingly monitoring the project progress. The past research on the accuracy of software function point counts has only addressed on the variation of function point counts. However, hardly any research to date has investigated the factors affecting the accuracy of function point counts and what identification rules are frequently misjudged and the reasons to cause misjudgment. Hence, the objective of this thesis is to explore how the factors of software development technique, software lifecycle stage, counter’s education background, software development experience, and education training of function point analysis method affect the accuracies of function point counts and also to find the solutions to avoid misjudgment of the identification rules of function point counts.
By deploying the case study of software function point counts and semi-structured interview with full-time and on-job master students at Department of Information Management, National Taiwan University of Science and Technology, the analysis result from 41 samples and 7 interviews indicates that the education training of function point analysis method has a significant influence on the accuracy of software function point count, but the factors of software development technique, software lifecycle stage, counter’s education background and software development experience do not have significant influences. This thesis also summarizes those frequently misjudged identification rules and the reasons to cause these misjudgments, and accordingly proposes the enhanced interpretations and implication guidelines for these rules. Base on the above findings, we consider the important factors affecting the accuracy of software function point counts are the completeness of software function requirement specification, the counter’s proficiency to function point analysis method and the domain knowledge in the developed software system.

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