中文摘要
社會大眾對大眾傳播媒體的表現一向是貶多於褒，然而這些對媒體的微辭又有何根據？大眾傳媒的表現又該如何評鑑？評鑑的標準又是怎樣？
本研究針對以上的問題，首先討論研究媒體表現之方向與步驟，接著就McQuail以「公共利益」為理論基礎所提出的「媒體表現分析模式」為分析大眾傳播媒體表現之標準加以討論，並以中央研究院社會學研究所籌備處於1998年7月執行的「台灣社會變遷基本調查計畫三期四次：大眾傳播組」以及研究者於1998年9月以輔入學的政大傳播學院大一新生為對象所進行的一項問卷調查兩筆實證資料，針對「媒體表現」中閱\聽大眾對於新聞傳播媒體之可信度加以分析。
本研究的研究問題有四：
1.什麼是可信度，不同媒介的可信度之間是否有異，各媒介可信度是否會因測量工具的不同而有差異。
2.閱\聽人評價可信度時會受到哪些因素影響。
3.可信度之於閱\聽人對社會真實的認知有何影響。
4.媒介新聞表現的內涵，其與可信度之間有何關聯。
本研究分析的結果如下：
電視新聞的可信度較報紙為高。
在影響可信度的因素方面，女性對報紙與電視可信度所作的評價較高，教育程度或個人收入較高的受訪者對報紙和電視可信度的評價較低。此外，年紀愈大、對電視新聞可信度的評價有升高的傾向。而就「比較法」方面報紙和電視孰較可信來做比較，女性較男性更相信電視，教育程度以及個人收入較高的受訪者較相信報紙。
就可信度對認知社會真實的影響而言，在認知「產業外移」方面，相較於認為新聞報導較實際情形嚴重，對有親身經驗的受訪者而言，對報紙可信度所作評價高，將媒介真實視為社會真實的可能性愈大，電視可信度在此的作用不顯著；相較於認為實際情形較新聞報導嚴重，不論受訪者有無親身經驗，對報紙可信度所作評價高，將媒介真實視為社會真實的可能性愈大，電視可信度與認知社會真實之間的正向關聯僅存在於沒有親身經驗的受訪者。在認知「暴力犯罪」方面，相較於認為新聞報導較實際情形嚴重，對沒有親身經驗的受訪者而言，對報紙可信度所作評價高，將媒介真實視為社會真實的可能性愈大，電視可信度在此的作用不顯著；相較於認為實際情形較新聞報導嚴重，不論受訪者有無親身經驗，不論報紙或電視新聞的可信度與認知社會真實之間都沒有顯著關聯。
媒介的新聞表現量表經因素分析，可得出五個共同因素：新聞品質、特殊利益、負面內容、倚賴和控制、形式。新聞品質這個共同因素所指涉的範圍與新聞可信度有相當重疊，可信度可視為是新聞表現的一個面向。
英文摘要
Media performance has been the center of social critic since the infancy of mass media. Yet, there has been no agreement of how to evaluate the media performance, less than what the evaluation criterion to be.
The purpose of this study is to provide a system to assess media performance. First, the approaches and procedures of media performance analysis are discussed. Then, McQuail ’s "analytic model of media performance," which is based on theories of "public interest," is proposed as a model to evaluate media performance. Based on this model, two sets of survey data are analyzed for the questions regarding to the "credibility" of news media. These questions are:
1.What is the "credibility?" Does the "credibility" differ from one medium to another? Does the "credibility" differ in different measurements?
2.What are the factors influencing audience ’s judgements of media credibility?
3.What is the relationship between audience ’s perceived media credibility and perceived social reality?
4.What is the relationship between media credibility and media performance?
Results of analyzing the two data sets are the following:
Regarding to factors influencing audience ’s judgements of media credibility: Female subjects tend to agree both TV and newspapers have higher credibility. Subjects with higher educated and income tend to evaluate credibility of TV and newspapers less. Older subjects evaluate TV ’s credibility higher.
To compare credibility of TV and newspapers, female subjects tend to believe TV more than male while subjects of higher education and income tend to believe newspapers more.
As for the relationship between audience ’s perceived media credibility and perceived social reality: Those who think news reports exaggerate more serious than reality and with personal experience tend to evaluate newspapers ’ credibility higher regarding to the issue of "industry export," while TV ’s credibility is not significant. Furthermore, in the same issue, those who, regardless personal experience, think reality is more serious than news reports tend to evaluate newspapers ’ credibility higher, while TV ’s credibility only positively relates to those who have no personal experience. On the issue of "violent crime", those who think news reports are more serious than reality and have no personal experience tend to evaluate newspapers ’ credibility higher, while credibility of TV has no significance. On the other hand, neither TV or newspapers ’ credibility indicates no significance for those who, regardless personal experience, think that reality is more serious than news reports.
Finally, a factor analysis of news media performance results five common factors--news quality, special interest, negative content, dependency and control, and format. Among these five factors, news quality overlaps with credibility, thus, credibility can be treated as part of news media performance.