期刊影響指數是近年來用來評估期刊重要性及影響力的一個指標。由期刊引用文獻評比報告，根據前兩年發表的文章之統計資料計算而得。例如2003年的期刊影響指數是根據2001以及2002發表的文章在2003年被引用的次數總合除以2001以及2002發表的文章總合所得之比值。在本論文中，我們檢驗了不同領域之間以及同領域內期刊影響指數的表現，也根據同領域內期刊被引用的趨勢去分群。我們也從統計分析的觀點提供了不同型態的期刊影響指數用來描述期刊的特性。

An impact factor(IF) has been used extensively as a measure of the importance and impact of journals recently. The IF
provided by the Journal Citation Reports (JCR) is calculated based on the most recent three years period. For example, the IF of 2003 for a journal is calculated; the number articles published in 2001 to 2002 cited in tracked journals during 2003 divided by the number of articles published in 2001 to 2002. In this work, we examine the
different patterns of IF of journals in different fields as well as within the same field. We also provide a method of clustering journals according to the characteristics of the corresponding IF within the same field. Based on the experiences from analyzing the IF, we propose modified IFs from statistics point of view as possible new measures for the characteristics of different journals.

1. Introduction..............................1
2. Data description and Cited Behavior.......1
3. New method and Comparison.................5
3.1 Cited Half-Life and Mode................5
3.2 Variance Reduction......................8
3.3 Comparison.............................10
4. Clustering and Ranking...................13
4.1 Clustering.............................13
4.2 Ranking................................17
4.3 Relative intensity of journals.........20
5. Conclusion...............................22
References..................................22
Appendix....................................23

[1] Albert R. (1998), Journal Price Study: Core Agricultural and Biological Journals, Ithaca, N.Y.: Faculty Taskforce, College of Agriculture and Life Sciences, Mann Library, Cornell University.

[2] Bergstrom, T.C. (2001), Free labor for costly journals, Journal of Economic Perspectives, 15, 183-198

[3] Case, M. M. (1999), Measuring the cost effectiveness of journals: The Wisconsin experience, ARL Bimonthly Report, 205, 1-6.

[4] Gust K. J. (2005), Evaluating the impact factor: A citation study for information techology journals, Michigan State University Information Systems, 6, 1-7.

[5] Podlubny, I. (2005), Comparison of scientific impact expressed by the number of citations in different fields of science, Scientometrics, 64, 95-99.

[6] Rencher, Alvin C. (2002), Methods of Multivariate Analysis, 2nd ed, Wiely N.Y.