Book contents
- Frontmatter
- Contents
- List of figures
- List of tables
- List of boxes
- Introduction
- Part I Effect sizes and the interpretation of results
- 1 Introduction to effect sizes
- 2 Interpreting effects
- Part II The analysis of statistical power
- Part III Meta-analysis
- Last word: thirty recommendations for researchers
- Appendices
- Bibliography
- Index
2 - Interpreting effects
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- List of figures
- List of tables
- List of boxes
- Introduction
- Part I Effect sizes and the interpretation of results
- 1 Introduction to effect sizes
- 2 Interpreting effects
- Part II The analysis of statistical power
- Part III Meta-analysis
- Last word: thirty recommendations for researchers
- Appendices
- Bibliography
- Index
Summary
Investigators must learn to argue for the significance of their results without reference to inferential statistics.
~ John P. Campbell (1982: 698)An age-old debate – rugby versus soccer
A few years ago a National IQ Test was conducted during a live TV show in Australia. Questions measuring intelligence were asked on the show and viewers were able to provide answers via a special website. People completing the online questionnaire were also asked to provide some information about themselves such as their preferred football code. When the results of the test were published it was revealed that rugby union fans were, on average, two points smarter than soccer fans. Now two points does not seem to be an especially big difference – it was actually smaller than the gap separating mums from dads – but the difference was big enough to trigger no small amount of gloating from vociferous rugby watchers. As far as these fans were concerned, two percentage points was large enough to substantiate a number of stereotypes regarding the mental capabilities of people who watch soccer.
How large does an effect have to be for it to be important, useful, or meaningful? As the National IQ story shows, the answer to this question depends a lot on who is doing the asking. Rugby fans interpreted a 2-point difference in IQ as meaningful, legitimate, and significant. Soccer fans no doubt interpreted the difference as trivial, meaningless, and insignificant.
- Type
- Chapter
- Information
- The Essential Guide to Effect SizesStatistical Power, Meta-Analysis, and the Interpretation of Research Results, pp. 31 - 44Publisher: Cambridge University PressPrint publication year: 2010
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