5.5.1.2. Continuous outcomes

If the 95%CI upper or lower CI crosses the minimally important difference (MID), either for benefit of harm.

Note: if the MID is not known or the use of different outcome measures required calculation of an effect size, we suggest downgrading if the upper or lower CI crosses an effect size of 0.5 in either direction.

Effect size (ES):

A generic term for the estimate of effect of treatment for a study. Sometimes, the term is used to refer to the standardized mean difference, the difference between two estimated means divided by an estimate of the standard deviation.

To facilitate the understanding we suggest an interpretation of the effect size offered by Cohen, also known as ‘Cohen’s d’[1]. According to this interpretation, an effect size or SMD of around:

• 0.2 is considered a small effect;
• 0.5 is considered a moderate effect;
• 0.8 or higher is considered a large effect.

There are also other methods to standardise effect sizes, such as Glass ∆ or hedges d, depending on the choice of the estimator of the standard deviation.

[1] (Cohen J. Statistical Power Analysis for the Behavioral Sciences. 2nd ed; 1988).