Hi, friend! As it is generally costly to collect survey data of patients, could you give me a clue about how to calculate the ideal number of participants?

Cheers.

Ok, I see. Cheers.

For most survey-based outcomes, evaluations typically need data from 20 to 100 patients per practice to be confident that they can detect a meaningful effect. Collecting survey data from more patients might increase the precision of estimates of a practice’s average outcome for its own patients, but it will only slightly improve the precision of the estimated effect for the intervention as a whole (that is, increase your ability to detect a small effect).