(δ) Effect size

[Guest guest]

Hello everybody,

Here I have also located δ i.e.Minimum expected difference (also known as the effect size)

It is the smallest measured difference between comparison groups that the investigator would like the study to detect. Sample size is inversely proportional to the effect size.

This parameter is subjective and is based on clinical judgment and experience with the problem being investigated. The results of pilot studies or a literature review can also guide the selection of a reasonable minimum difference.

For example, suppose a study is designed to compare a standard antimicrobial drug with 80% cure rate with a new antimicrobial agent of unknown but potentially higher cure rate. It would probably be clinically unimportant if the new drug would only have 81% cure rate, but suppose the investigator believes that it would be a clinically important improvement if the new drug would have 90% cure rate. Therefore, the investigator would choose a minimum expected difference of 10% (0.10).

So in this case finding the smaller difference is of no value. Thus it is the clinical judgement and problem under investigation is important.

Regards,

Dr. Smita Mali