Eiken Kobai and George Gatenby can - if you will listen deeply to what they have to say, and lay aside self-powered calculation as you do.
Those who are susceptable (as almost all of us are) - who have a place where pride of ownership leaves them open to choosing self-powered calculation over simple hearing, will insist that somehow they bring something to the table when it comes to the dharma.
However, the numbers of patients included in our current study are not sufficiently large to carry out a high-powered calculation.
Post-hoc power calculation showed the study being adequate powered (88%) to negate our hypothesis that c.-1973T > C is associated with liver disease of various aetiologies (α = 0.05, difference in group proportions 10% (20% and 30%)).
Hence, we decided to pursue a fully powered trial, with the main phase (MP) power calculation based on the mean difference in AUDIT scores (the primary outcome) between the two groups at the end of the run-in phase.
In a study in which mortality is the primary outcome, overestimating the mortality rate in the power calculation will result in the study being under-powered.
The reviewers assessed power calculations as being 'done' where there was evidence of a power calculation being conducted, 'not clear' if it was not reported and 'not done' if the authors specifically report that the study was under-powered.
A revised power calculation estimated that, at 5% significance and 80% power, the 145 participants actually recruited would enable the trial to detect a difference of 0.47 standard deviation units (~20% larger than the originally powered difference).
Nevertheless, the potential cost savings and prevention of doing an under-powered study, by using the studied simulation-based power calculations method, are worth the computational time and cost.
Post hoc power calculations were carried out to evaluate whether the study was sufficiently powered, and to inform future research.
Post-hoc power calculations indicated that this study of the psychometric properties of the new iCAHE instrument was under-powered (0.49) and should therefore be considered as a pilot.
