(I did not downvote) I have also observed people suggest a statistically special N, but this is a misconception. There is no special N. There is only a relatio

(I did not downvote) I have also observed people suggest a statistically special N, but this is a misconception. There is no special N. There is only a relationship between increasing N and a monotonic increase in the confidence in your result. Most scientific standards specify a "confidence" of at least 95%, but if you are willing to accept more uncertainty--perhaps because there is a large upside to a positive result--then you can make due with a smaller sample.