Our power estimates are only as good as our effect size estimates. We should give some thought to what size effects are of interest in the context of our research. Some will argue that in the exploratory stages of research we cannot know how large an effect to expect. This is true, but we can almost always specify the minimum effect that would be of interest. Some will argue that even this minimum effect is sometimes impossible to specify.
Any inferential analysis becomes a mere mental exercise with no merit.
A better choice would be to perform exploratory data analyses, with emphases on parameter and effect size estimation. Such estimation is uniformly preferable to NHT in any situation. Michael E. Walker, April 1999.