Predictors of publication in Dental Research. The analysis of clinical trials from 2005-2007. Thesis submitted in accordance with the requirements of the University of Liverpool in partial fulfilment for the degree of Doctorate in Dental Science by Gareth Williams. September 2012 Table of Contents Acknowledgements ...................................................................................................... 6 Structured Abstract....................................................................................................... 7 Aims: ..................................................................................................................................................................... 7 2005-2007 abstracts ........................................................................................................................................... 7 University Teachers Group (UTG) abstracts .......................................................................................... 8 Design: ..................................................................................................................................................................... 8 Subject and Setting: ............................................................................................................................................ 8 Sample size ............................................................................................................................................................. 9 Method: .................................................................................................................................................................... 9 Results:..................................................................................................................................................................... 9 Conclusions: ........................................................................................................................................................ 10 Chapter 1 - Introduction ............................................................................................. 11 Chapter 2 – Literature Review ................................................................................... 14 Evidence Based Practice and Publication Bias:................................................................................ 14 Why does publication bias exist? ........................................................................................................... 24 Academic journals ........................................................................................................................................ 24 The Impact Factor ........................................................................................................................................ 26 Why is this important? ............................................................................................................................... 27 Setting the scene ........................................................................................................................................... 29 Previous work ................................................................................................................................................ 30 Study design ......................................................................................................................................................... 30 Significance of results ...................................................................................................................................... 31 Presentation at conferences .......................................................................................................................... 33 Country of origin ............................................................................................................................................... 33 Gender of primary author .............................................................................................................................. 33 Disclosure of funding ....................................................................................................................................... 34 Sample size ........................................................................................................................................................... 34 Submission email (institutional or personal) ......................................................................................... 34 Primary author’s status .................................................................................................................................. 34 Publication rates ................................................................................................................................................ 34 Time to publication ........................................................................................................................................... 35 Reasons for failure to progress to full publication .............................................................................. 36 Calibration ....................................................................................................................................................... 38 Reliability ......................................................................................................................................................... 38 Aims ......................................................................................................................................................................... 38 Null hypothesis ................................................................................................................................................... 39 Method ................................................................................................................................................................... 39 Sample size ........................................................................................................................................................... 39 Source of abstracts ............................................................................................................................................ 40 Identification of abstracts: ............................................................................................................................. 40 Inclusion criteria: .............................................................................................................................................. 40 Exclusion criteria .............................................................................................................................................. 40 2 Assessments .......................................................................................................................................................... 41 Data collection ................................................................................................................................................... 41 Statistical methods ............................................................................................................................................ 41 Random selection ............................................................................................................................................... 42 Results of Reliability Study ............................................................................................................................ 43 Discussion ............................................................................................................................................................. 45 Conclusion ............................................................................................................................................................ 45 Chapter 4 – Main investigation .................................................................................. 46 Aims: .................................................................................................................................................................. 46 2005-2007 abstracts ......................................................................................................................................... 46 University Teachers Group (UTG) abstracts ........................................................................................ 47 Objectives: ....................................................................................................................................................... 47 Null Hypotheses ............................................................................................................................................ 48 2005 – 2007 sample .......................................................................................................................................... 48 UTG sample ......................................................................................................................................................... 48 Chapter 5 - Method .................................................................................................... 50 Design: .............................................................................................................................................................