Original Research

The use of effect size indices to determine practical significance

H. S. Styn jr., S. M. Ellis
Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie | Vol 25, No 3 | a157 | DOI: https://doi.org/10.4102/satnt.v25i3.157 | © 2006 H. S. Styn jr., S. M. Ellis | This work is licensed under CC Attribution 4.0
Submitted: 22 September 2006 | Published: 22 September 2006

About the author(s)

H. S. Styn jr., Statistiese Konsultasiediens, Noordwes-Universiteit, South Africa
S. M. Ellis, Statistiese Konsultasiediens, Noordwes-Universiteit, South Africa

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The determination of significance of differences in means and of relationships between variables is of importance in many empirical studies. Usually only statistical significance is reported, which does not necessarily indicate an important (practically significant) difference or relationship. With studies based on probability samples, effect size indices should be reported in addition to statistical significance tests in order to comment on practical significance. Where complete populations or convenience samples are worked with, the determination of statistical significance is strictly speaking no longer relevant, while the effect size indices can be used as a basis to judge significance. In this article attention is paid to the use of effect size indices in order to establish practical significance. It is also shown how these indices are utilized in a few fields of statistical application and how it receives attention in statistical literature and computer packages. The use of effect sizes is illustrated by a few examples from the research literature.


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